ANSWERS 


PRACTICAL  QUESTIONS  AND  PROBLEMS 


CONTAINED    IN 


THE  FOURTEEN  WEEKS  COURSES 


Physiology,  Philosophy,  Astronomy,  and 

Chemistry  (Old  and  New  Edition), 


BY 

;p°DORMAN   STEELE,  PH.D.,  F.G.S., 

AUTHOR   OF  THE   FOURTEEN   WEEKS   SERIES   If!   PHYSIOLOGY,    PHILOSOPHY, 
fl  ASTRONOMY,   AND*  (JEOLOGY. 


A.   S.   BARNES    &    COMPANY, 
NEW  YORK  AND  CHICAGO. 


THE    FOURTEEN   WEEKS'   COURSES 

IN 

NATURAL     SCIENC 

BY 

J.    DORMAN    STEELE,    A.M.,    Pn.D. 

Fourteeij  Weeks  iij  Natural  Ptylosopty, 
Fourteeij  Weeks  iij  Cljenjistry, 
Fourteeij  Weeks  iij  Descriptive  Astroijonjy, 
Fourteeij  Weeks  iij  Popular  Geology, 
Fourteeij  Weeks  iij  Human  Physiology, 
Fourteeij  Weeks  iij  Zoology, 
Fourteerj  Weeks  in  Botany, 

A  Key,   containing   Answers   to  the   Questions 
and  Problems  in  Steele's  14  Weeks'  Courses, 


SERIES, 

ON  THE  PLAN  OF  STEELE'S  14  WEEKS  IN  THE  SCIENCES. 

A  Brief  hjistory  of  the  United  States, 
A  Brief  F|istory  of  Fraijce, 


The  same  publishers  also  offer  the  following  standard  scientific 
works,  being  more  extended  or  difficult  treatises  than  those  of 
Prof.  Steele,  though  still  of  Academic  grade. 

Peck's  Ganot's  Natural  Philosophy, 
Porter's  Principles  of  Chemistry, 
Jarvis'  Physiology  and  Laws  of  Healtfy 
Wood's  Botanist  and  Florist, 
djanjbers'  Elements  of  Zoology, 
tyclij  tyre's  ^stro$)tfty  and 
Page's  Elenjents  of  GeologJ,  *s 


tDUCATJON  DEPT. 


Entered  according  to  Act  of  Congress,  in  the  year  1869,  by 

A.    S.     BARNES    &    CO., 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States 
for  the  Southern  District  of  New  York. 

STEELS' s  JCPY. 


PREFACE. 


THIS  little  work  is  designed  to  aid  teachers  who  are  using 
the  Fourteen  Weeks  Course.  The  problems  contained  in 
all  the  books  are  fully,  and,  it  is  thought,  accurately  solved. 
Great  pains  have  been  taken  to  revise  and  compare  them 
carefully.  The  practical  questions  are  answered,  often  not 
in  full,  yet  enough  so  to  give  the  key  to  the  more  perfect 
reply.  The  use  of  the  text-books  is  presupposed,  and  the 
statements  merely  supplement,  or  apply  the  fuller  theories 
therein  contained  and  explained.  On  many  points  there 
may  be  a  difference  of  opinion.  The  author  often  finds  in 
his  own  classes  a  wide  diversity.  On  mooted  questions  he 
has  merely  advanced  one  view,  leaving  the  subject  open 
for  the  discussion  of  other  theories.  Minute  directions  are 
given,  pages  71-82  inclusive,  for  performing  a  course  of 
experiments  in  Chemistry.  It  is  hoped  that  these  may  be 
of  service  to  teachers  who,  with  incomplete  apparatus,  are 
trying  to  illustrate  to  their  pupils  some  of  the  principles  cf 
that  science.  In  all  cases  of  doubt  or  misunderstanding 
with  regard  to  the  answers  or  solutions,  the  author  will  be 
pleased  to  correspond  with  any  teacher  using  the  Series 

ELMIRA,  March  19,  1870 


ANSWERS 

TO  THE  PEACTICAL  QUESTIONS 

m  THE 

FOURTEEN  WEEKS   COURSE 

IN 

NATURAL    PHILOSOPHY. 


|.The  bold-faced  figures  refer  to  the  pages  of  the  Philosophy ;  the  others  to 
the  number  of  th«.  Practical  Questions.] 


INERTIA. 

26.  I.  If  one  is  riding  rapidly,  in  which  direction  will  he 
be  thrown  when  the  horse  is  suddenly  stopped  ? 

In  the  same  direction  in  which  he  is  going.  He  has  the 
motion  of  the  carriage,  and  his  inertia  carries  him  forward. 

2.  When  standing  in  a  boat,  why,  as  it  starts,  are  we  thrown 
backward  ? 

Because  the  inertia  of  our  bodies  keeps  them  stationary, 
while  the  boat  carries  our  feet  forward. 

3.  When  carrying  a  cup  of  tea,  if  we  move  or  stop  quickly, 
why  is  the  liquid  liable  to  spill? 

The  inertia  of  the  tea  tends  to  keep  it  still  or  in  motion,  as 
the  case  may  be.  If  we  move  the  cup  quickly,  the  motion  is 
not  imparted  to  the  liquid  soon  enough  to  overcome  the 
inertia.  When,  therefore,  we  start,  the  tea  spills  out  back- 
ward; or,  when  we  stop,  it  spills  out  forward.  We  under- 
stand this  if  we  can  tell  why  a  cup  of  tea  is  more  liable  to  spill 
than  one  of  sugar. 


ANS^JKS  TO  PRAVT1VAL   QUESTIONS 


4.  Why  &>,fofrlo.d$*pfr'r'sued,  \cctn  we.  escape  by  dodging? 
We  turn  sharply.  '  O'ur  pursuer,  ignorant  of  our  design, 

cannot  overcome  his  inertia  so  as  to   turn  as  quickly,  and 
hence  is  carried  past. 

5.  Why  is  a  carriage  or  sleigh  ,  when  sharply  turning  a 
corner,  liable  to  tip  over  f 

Because  its  inertia  tends  to  carry  it  directly  forward.  A 
puzzling  question  in  this  connection  is  —  Why  is  a  sleigh  more 
liable  to  tip  over  than  a  wagon  ? 

6.  Why,  if  you  place  a  card  on  your  finger,  and  on  top  of  it 
a  cent,  can  you  snap  the  card  from  under  the  cent  'without 
knocking  the  latter  off  your  finger? 

Because  the  friction  between  the  card  and  the  cent  is  so 
slight  that,  by  a  quick  snap,  you  can  overcome  the  inertia  of 
the  former  without  imparting  any  force  to  the  latter. 

7.  Why  }  after  the  sails  of  a  vessel  are  furled,  does  it  still 
continue  to  move;  and  why,  after  the  sails  are  all  spread, 
does  it  require  some  time  to  get  under  full  headway? 

Its  inertia  must  be  overcome  in  the  one  case  by  the  resist- 
ance of  the  air  and  water,  and  in  the  other  by  the  force  of  the 
wind. 

COHESION. 

4O.  i  .  Why  can  we  not  weld  a  piece  of  copper  to  one  of 
iron  ? 

Cohesion  acts  only  between  molecules  of  the  same  kind. 

2.  Why  is  a  bar  of  iron  stronger  than  one  of  wood? 
Because  its  force  of  cohesion  is  stronger. 

3.  Why  is  a  piece  of  iron,  when  perfectly  welded,  stronger 
than  before  it  was  broken  f 

By  the  hammering,  more  particles  are  brought  within  the 
range  of  cohesion. 

4.  Why  do  drops  of  different  liquids  vary  in  size  f 
Because  they  vary  in  cohesive  force. 

5.  Why,  when  you  drop  medicine,  will  the  last  few  drops 
contained  in  the  bottle  be  of  a  larger  size  than  the  others  ? 


/2V  NATUKAL  PHILOSOPHY.  7 

The  pressure  of  the  liquid  in  the  bottle  is  less,  and  therefore* 
they  form  more  slowly. 

6.  Why  are  drops  larger  if  you  drop  them  slowly  ? 

There  is  more  time  for  the  adhesive  force  of  the  bottle  to 
act  on  the  liquid,  and  so  a  larger  drop  can  be  gathered. 

7.  Why  is  a  tube  stronger  than  a  rod  of  the  same  weight? 
Let  a  rod  supported  at  both  ends  be  broken  in  the  middle. 

We  shall  see  that  it  yields  first  on  the  circumference.  So  true 
is  this,  that  long  beams  heavily  loaded  have  been  broken  by  a 
mere  scratch  of  a  pin  on  the  lower  side.  The  particles  along 
the  centre  break  last.  They  rather  aid  in  the  fracture,  since 
they  afford  a  fulcrum  for  the  rest  of  the  rod,  acting  as  the  long 
arms  of  a  lever,  to  act  upon.  In  a  tube  the  particles  at  the 
centre  are  removed  and  all  concentrated  at  the  outside,  where 
the  first  strain  is  felt.  (See  Physiology,  p.  20). 

8.  Why,  if  you  melt  scraps  of  zinc ',  will  they  form  a  solid 
mass  when  cooled? 

The  heat  overcomes,  in  part,  the  attraction  of  cohesion,  so 
that  the  particles  flow  freely  on  each  other.  They  now  all 
come  within  the  range  of  cohesion,  so  that  when  the  metal 
cools  they  are  held  by  that  force  in  a  solid  mass. 

9.  In  what  liquids  is  the  force  of  cohesion  greatest? 
Mercury,  molasses,  etc. 

10.  Name  some  solids  that  will  volatilize  without  melting  f 
Arsenic,  camphor. 

ADHESION. 

47.  i.  Why  does  cloth  shrink  when  wet? 

By  capillary  attraction  the  water  is  drawn  into  the  pores  01 
the  cloth.  The  fibres  are  thus  expanded  sidewise  and  short- 
ened lengthwise.  The  cloth  "fulls  up"  or  thickens  while  it 
shortens  and  narrows  (shrinks)  in  the  process. 

2.   Why  do  sailors  at  a  boat-race  wet  the  sails  ? 
The  pores  being  full  and  expanded  make  the  sails  more  com- 
pact.    They  will  therefore  hold  the  wind  better. 


8  ANSWERS  TO  PRACTICAL  QUESTIONS 

3.  Why  does  not  writing-paper  blot? 

Because  the  pores  are  filled  with  size.  (See  Chemistry, 
p.  161.) 

4.  Why  does  paint  prevent  wood  from  shrinking? 
Because  it  fills  the  pores  of  the  wood. 

5.  What  is  the  shape  of  the  surface  of  a  glass  of  water  and 
one  of  mercury  f 

Ordinarily  the  former  is  concave  and  the  latter  convex. 

6.  Why  can  we  not  dry  a  towel  perfectly  by  wringing  ? 
Because  of  the  strength  of  the  capillary  force  by  which  the 

water  is  held  in  the  pores  of  the  cloth. 

x 

7.  Why  will  not  water  run  through  a  fine  sieve  when  the 
wires  have  been  greased? 

Because  the  grease  repels  the  water  and  so  prevents  capil- 
lary action. 

8.  Why  will  camphor  dissolve  in  alcohol  and  not  in  water? 
Because  there  is  a  strong  adhesion  between  the  alcohol  and 

camphor,  and  little,  if  any,  between  the  water  and  camphor. 

9.  Why  will  mercury  rise  in  zinc  tubes  as  water  does   in 
glass  tubes  ? 

Because  of  the  strong  adhesion  between  zinc  and  mercury. 

10.  Why  is  it  so  difficult  to  lift  a  board  out  of  water  ? 
Because  of  the  adhesion  between  the  board  and  the  water. 

1 1 .  Why  will  ink  spilled  on  the  edge  of  a  book  extend  further 
inside  than  if  spilled  on  the  side  of  the  leaves? 

Because  the  capillary  pores  of  the  paper  are  short,  being 
only  the  thickness  of  a  leaf,  while  the  capillary  spaces  between 
the  leaves  are  longer  and  continuous. 

12.  If  you  should  happen  to  spill  some  ink  on  the  edge  of 
y cur  book,  ought  you  to  press  the  leaves  together? 

No.  Because  you  would  make  the  capillary  spaces  between 
the  leaves  smaller,  and  so  the  ink  would  rise  in  them  further. 

13.  Why  can  you  not  mix  oil  and  water  ? 
Because  there  is  no  adhesion  between  them. 


IN  NATURAL  PHILOSOPHY.  9 

15.  Why  will  water  wet  your  hand  while  mercury  will  not? 
Because  in  the  former  case  there  is  an  adhesion,  in  the 
latter  none. 

1 6  Why  is  a  tub  or  pail  liable  to  fall  to  pieces  if  not  filled 
with  water  or  kept  in  the  cellar? 

Because  the  moisture  dries  out  of  the  pores,  and  the  wood 
shrinks  so  as  to  let  the  hoops  fall  off. 

17.  Name  instances  where  the  attraction  of  adhesion  h 
stronger  than  that  of  cohesion. 

Wood  fastened  by  glue  will  often  split  before  the  glue  will 
yield.  Paper  stuck  with  paste,  and  bricks  with  mortar,  are  also 
examples. 

GRAVITATION. 

63.  i.  When  an  apple  falls  to  the  ground ^  how  much  does 
the  earth  rise  to  meet  it? 

The  earth  falls  as  much  less  distance  than  the  apple,  as  its 
weight  is  greater. 

2.  What  causes  the  sawdust  in  a  mill-pond  to  collect  in  large 
masses  ? 

The  attraction  of  gravity  which  exists  between  all  bodies, 
whereby  they  attract  each  other.  All  bodies  on  the  earth 
would  tend  to  approach  each  other,  and  the  big  ones  would 
gather  all  the  little  ones  around  them  were  they  as  free  to  move 
as  the  sawdust  floating  on  water. 

3.  Will  a  body  weigh  more  in  a  valley  than  on  a  mountain  f 
It  will,  because  the  attraction  of  the  earth  is  greater. 

4.  Will  a  pound  weight  fall  more  slowly  than  a  two-pound 
weight  ? 

They  will  both  fall  in  the  same  time,  except  the  slight 
difference  which  is  caused  by  the  resistance  of  the  air.  Galileo 
propounded  this  view  and  proved  it,  in  the  presence  of  a  vast 
crowd,  by  letting  unequal  weights  fall  from  the  leaning  tower 
of  Pisa. 


IO  ANSWERS  TO  PRACTICAL  QUESTIONS 

5.  How  deep  is  a  well,  if  it  takes  three  seconds  for  a  stone  to 
fall  to  the  bottom  of  it  ? 

(2)  equation  of  falling  bodies,  d  =  1W ;  hence  d  =  16  x  3a  a  144  feet. 

_6.  Is  the  centre  of  gravity  always  within  a  body — as ',  for 
example,  a  ring? 

It  is  not.     In  the  case  given  it  is  at  the  centre  of  the  circle. 

7.  If  two  bodies,  weighing  respectively  i  and  4  pounds,  be 
connected  by  a  rod  24  inches  long,  where  is  the  centre  of  gravity  ? 

To  be  In  equilibrium  the  weight  of  one  multiplied  by  its  distance  from  the 
c«:nt-re  of  gravity  must  equal  the  weight  of  the  other  multiplied  by  its  distance. 
24  -+-  6  =  4 ;  hence  4  in.  is  the  unit  for  each  pound.  Therefore  the  centre  of 
gravity  is  8  in.  from  the  larger  weight  and  16  in.  from  the  smaller. 

-  8.  In  a  ball  of  equal  density  throughout,  where  is  the  centre 
of  gravity  ? 

At  the  centre  of  the  ball. 

9.  Why  does  a  ball  roll  down  hill? 

Because  the  line  of  direction  falls  without  the  small  base  of  the 
ball. 

10.  Why  is  it  easier  to  roll  a  round  body  than  a  square  one  f 
Because  the  base  of  the  ball  is  so  much  smaller,  and  therefore 

the  centre  of  gravity  need  not  be  raised  to  bring  the  line  of  di- 
rection without. 

1 1.  Why  is  it  easier  to  tip  over  a  load  of  hay  than  one  of 
stone  ? 

Because  the  centre  of  gravity  in  a  load  of  hay  is  very  high, 
and  in  a  load  of  stone  very  low.  Therefore  the  centre  of 
gravity  in  the  former  need  not  be  raised  much  to  bring  the 
line  of  direction  without  the  base,  while  in  the  latter  it  must  be. 

12.  Why  is  a  pyramid  the  stablest  of  structures  ? 

Because  the  base  is  so  broad  and  the  centre  of  gravity  so 
low.  The  centre  of  gravity  must  therefore  be  lifted  very  high 
before  the  line  of  direction  will  fall  without  the  base. 

13.  When  a  hammer  is  thrown,  on  which  end  does  it  always 
strike  f 

On  the  heavy  end  or  head,  because  that  part  is  attracted  by 
the  earth  more  strongly. 


IN  NATURAL  PHILOSOPHY.  I  J 

14.  Why  does  a  rope-walker  carry  a  heavy  balancing-pole  ? 
Because  in  this  way  he  can  easily  shift  his  centre  of  gravity. 

15.  What  would  become  of  a  ball  if  dropped  i*ito  a  hole 
bored  through  the  centre  of  the  earth  ? 

In  falling,  it  would  gain  a  momentum  which  would  carry  it 
past  the  centre  of  the  earth.  But  as  it  is  constantly  coming 
to  a  part  having  a  slower  axial  revolution  than  itself,  it  would 
scrape  on  the  east  side  of  the  hole  until  it  reached  the  centre ; 
beyond  that  point  it  would  scrape  on  the  west  side.  This 
friction  would  prevent  its  reaching  the  opposite  side  of  the 
earth.  It  would  therefore  vibrate  to  and  fro,  each  time  through 
a  shorter  distance,  until,  at  last,  it  would  come  to  rest  at  the 
centre  of  the  earth. 

1 6.  Would  a  clock  lose   or  gain  time  if  carried  to  the  top  of 
J  a  mountain  ? 

It  would  lose  time,  because  the  force  of  gravity  would  be 
lessened.  At  the  North  Pole  it  would  gain  time,  because  there 
the  force  of  gravity  would  be  increased. 

1 7.  In  the  winter,  would  you  raise  or  lower  the  pendulum- 
bob  of  your  clock  ? 

I  would  lower  it,  since  the  cold  of  winter  shortens  the  pen- 
dulum, and  this  movement  of  the  bob  would  counteract  that 
change. 

1 8.  Why  is  the  pendulum-bob  always  made  flat? 
To  decrease  the  friction  of  the  air. 

19.  What  beats  off  the  time  in  a  watch  f 
The  vibration  of  the  balance-wheel. 

20.  Is  solved  in  the  book. 

21.  What  should  be  the  length  of  a  pendulum  at  New  YorA 
to  vibrate  half-seconds  ? 

(1  sec.)»  :  (Va  sec.)2  : :  39.1  in.  :  x  =  9.7  +  inches. 
To  vibrate  quarter-seconds  ? 

(1  sec.)'  :  (V4  sec.)'  : :  39.1  in.  :  x  =  2.4  +  inches. 
To  vibrate  hours  f 

(1  sec.)3  :  (3600  sec.)3  : :  39.1  in.  :  x  -  7997.7  miles.* 

*  Nearly  the  diametor  of  the  earth. 


12  ANSWERS  TO  PRACTICAL   QUESTIONS 

22.  What  is  the  proportionate  time  of  vibration  of  two  pen* 
dulutns^  1 6  and  64  inches  long,  respectively  ? 

According  to  the  third  law  of  pendulums, 
Time  of  vib.  of  1st  :  Time  of  vib.  of  2d  : :  v/16  :  v/64  : :  4  :  8  : :  1  :  2. 

23.  Why,  when  you  are  standing  erect  against  a  wall,  and 
a  piece  of  money  is  placed  between  your  feet,  can  you  not  stoop 
forward  and  pick  it  up  ? 

By  leaning  forward  you  bring  the  centre  of  gravity  in  front 
of  your  feet,  and,  as  on  account  of  the  wall,  you  cannot  throw 
any  part  of  your  body  back  to  preserve  the  balance,  you  fall 
forward. 

24.  If  a  tower  were  198  feet  high,  with  what  velocity  would 
a  stone  dropped  from  the  summit,  strike  the  ground  f 

According  to  equation  (3),  t>2  =  64  d.    t?2  =  64  x  198.    0=112.5  feet. 

25.  A  body  falls  in  5  seconds :  with  what  velocity  does  it 
strike  the  ground? 

According  to  equation  (1),  v  =  32  t.    v  =32  x  5.    v  =160  feet. 

26.  How  far  will  a  body  fall  in  10  seconds  ? 

According  to  equation  (2),  d  =  16  £2.  d  =  16  x  102  =  1600  feet. 
With  what  velocity  will  it  strike  the  ground? 

According  to  equation  (1),  v  =  32  t.    v  =  32  x  10  =  320  feet. 

27.  A  body  is  thrown  upward  with  a  velocity  of  192  feet  the 
first  second ;  to  what  height  will  it  rise  ? 

Equation  (1),  v  =  32  t.    192  =  32  t.  t  =  Q  sec. 

(2),  d  =  16  P.    d  =  16  x  62=576  feet. 

28.  A  ball  is  shot  upward  with  a  velocity  of  256  feet ;  to 
what  height  will  it  rise  ?    How  long  will  it  contin ue  to  ascend  f 

Using  equations  (1)  and  (2),  as  in  the  last  problem,  we  hare  : 

t  =  8  sec. 
d  =  1024  feet. 

30.  Are  any  two  plumb-lines  parallel? 
They  are  not,  since  they  all  point  to  the  centre  of  the  earth. 
No  two  spokes  of  a  wheel  can  be  parallel 


IN  NATURAL  PHILOSOPHY.  13 

31.  A  stone  let  fall  from  a  bridge  strikes  the  water  in  three 
seconds.      What  is  the  height  ? 

Equation  (2),  d  =  16t\    d  =  16  x  39  =  144  feet. 

32.  A  stone  falls  from  a  church  steeple  in  4  seconds.    What 
is  the  height? 

Equation  (2),  d  =  16*a.    d  =  16  x  4s  =  256  feet. 

33.  How  far  would  a  body  fall  the  first  second  at  a  height 
of  12,000  miles  above  the  earth's  surface? 

(16,000  mi.)a  :  (4000  mi,)2  : :  16  feet  :  x  =  1  foot. 

34.  A  body  at  the  surf  ace  of  the  earth  weighs  100  tons  : 
what  would  be  its  weight  1 ,000  miles  above  ? 

,(5000  mi.)3  :  (4000  mi.)2  : :  100  tons  :  x  =  64  tons. 

35.  A  boy  wishing  to  find  the  height  of  a  steeple  lets  fly  an 
arrow  that  just  reaches  the  top  and  then  falls  to  the  ground. 
It  is  in  the  air  6  seconds.     Required  the  height. 

Equation  (2),  d  =  16<a.    d  =  16  x  3*  =  144  ft. 

36.  A  cat  let  fall  from  a  balloon  reaches  the  ground  in  10 
seconds.     Required  the  distance. 

Equation  (2),  d  =  16  x  10a  =  1600  ft, 

37.  In  what  time  will  a  pendulum  40  feet  long  make  a 
vibration  f 

According  1o  the  third  law  of  pendulums,  and  taking  the  length  of  a  seconds 
pendulum  as  39  in.,  we  have : 

1  sec.  :  x  : :  V§9  :  1/40x12  in. 


x  =  3.5+  sec. 


—  In  what  time  will  a  pendulum  52  feet  long  make  a  vi« 
bration? 


14  ANSWERS  TO  PRACTICAL  QUESTIONS 

—How  long  would  it  take  for  a  pendulum  one  mile  in  length 
to  make,  a  vibration  ? 

— How  long  would  it  take  for  a  pendulum  reac  king  from 
the  earth  to  the  moon  to  make  a  vibration  ? 

— Required  the  length  of  a  pendulum  that  would  vibrate 
centuries.  (  70  be  solved  like  problem  20. ) 

38.  Two  meteoric  bodies  in  space  are  12  miles  apart.     They 
weigh    100  and    200    Ibs.    respectively.     If  they  should  fall 
together  by  force  of  their  mutual  attraction,  what  portion  of 
the  distance  would  be  passed  over  by  each  body  ? 

The  distance  passed  over  by  the  two  bodies  is  inversely  as 
their  mass;  hence  one  moves  8  miles  and  the  other  4  miles. 

39.  If  a  body  weighs  2,000  Ibs.  upon  the  surface  of  the  earth, 
what  would  it  weigh  2,000  miles  above  ? 

(6000  mi.)2  :  (4000  mi.)3  : :  2000  Ibs. :  x  =  888*/«  Ibs. 
•  How  much  500  miles  above? 

(4500  mi.)2  :  (4000  mi.)3  : :  2000  Ibs.  :  x  =  1580+ Ibs. 
The  weight  of  bodies  below  the  surface  of  the  earth  de- 
creases as  the  distance  increases.    Ex.  :  What  would  the  above 
body  weigh  if  carried  2 ,  ooo  miles  below  the  surface  ?     I ,  ooo  Ibs. 
— i ,  ooo  m  iles  below  ?     i ,  5  oo  Ibs. 

40.  At  what  distance  above  the  surface  of  the  earth  will  a 
body  fall,  the  first  second,  2 1  \  inches  ? 

A  body  falls  16  ft.*  (192  inches)  at  the  surface  of  the  earth.  21 1/3  inches  are 
:/9  of  192  inches  :  Now  as  the  attraction  is  inversely  as  the  square  of  the  dis- 
tance, the  distance  must  be  v/9,  or  3  times  that  at  the  surface.  Hence  the  body 
must  be  12,000  miles  from  the  centre,  or  8,000  miles  from  the  surface  of  the 
earth.  The  problem  may  be  solved  directly  by  proportion,  thus : 

a2  :  40002  : :  192  inches  :  21  Vs  inches. 

*  =  12000  miles  (distance  from  the  centre) 

12000  miles— 4000  miles =8000  miles. 

41.  How  far  will  a  body  fall  in  8  seconds?     1,024  ft. — In 
the  %th  second?    240  ft. — In  10  seconds?     1,600  ft. — In  th* 
30^  second?    944  ft. 

*  According  to  the  best  authorities  the  distance  is  more  exactly  16l/ir  ft. 


IN  NA  TUB  A  L  PHILOSOPHY.  I  5 


MOTION. 

8O.  i.  Can  a  rifle-ball  be  fired  through  a  handkerchief  sus- 
pended loosely  from  one  corner? 

Yes.   The  wind  of  the  ball  will  lift  the  handkerchief  somewhat. 

2.  A  rifle-ball  thrown   against  a  board  standing  edgewise 
will  knock  it  down  j  the  same  bullet  fired  at  the  board  will 
pass  through  it  "without  disturbing  its  position.      Why  is  this? 

The  ball  which  is  thrown  has  time  to  impart  its  motion  to 
the  board ;  the  one  fired  has  not. 

3.  Why  can  a  boy  skate,  safely  over  a  piece  of  thin  ice,  when, 
if  he  should  pause,  it  would  break  under  him  directly  ? 

In  the  former  case  there  is  time  for  the  weight  of  his  body  to 
be  communicated  to  the  ice ;  in  the  latter,  there  is  not. 

4.  Why  can  a  cannon-ball  be  fired  through  a  door  standing 
ajar,  without  moving  it  on  its  hinges  ? 

Because  the  cannon-ball  is  moving  so  quickly  that  its  motion 
is  not  imparted  to  the  door. 

5.  Why  can  we  drive  on  the  head  of  a  hammer  by  simply 
striking  the  end  of  the  handle  ? 

This  can  only  be  done  by  a  quick,  sharp  blow  which  will 
drive  the  wooden  handle  through  the  socket  before  the  motion 
has  time  to  overcome  the  inertia  of  the  iron  head.  A  slow, 
steady  blow  will  be  imparted  to  the  head,  and  so  fail  of  the 
desired  effect. 

6.  Suppose  you  were  on  a  train  of  cars  moving  at  the  rate 
oj '30  miles  per  hour :  with  what  force  would  you  be  thrown 
forward  if  the  train  were  stopped  instantly? 

With  the  same  velocity  which  the  train  had,  01  44  feet  pet 
second.  Your  momentum  would  be  your  weight  avoirdupois 
multiplied  by  this  velocity. 

7.  In  what  line  does  a  stone  fall  from  the  mast-head  of  a 
vessel  in  motion  ? 

In  a  curved  line,  produced  by  the  two  forces — gravity  and 
the  forward  motion  of  the  vessel. 


1 6  ANSWERS  TO  PRACTICAL   qUESTlONS 

8.  If  a  ball  be  dropped  from  a  high  tower  it  will  strike  the 
earth  a  little  east  of  a  vertical  line.      IV hy  is  this  ? 

In  the  daily  revolution  of  the  earth  on  its  axis,  from  west  to 
east,  the  top  of  the  tower  moves  faster  than  the  bottom,  be- 
cause it  passes  through  a  larger  circle.  When,  therefore,  the 
ball  falls,  it  retains  that  swifter  easterly  motion  and  so  strikes 
east  of  the  vertical. 

9.  //  is  stated  that  a  suit  was  once  brought  by  the  driver  of 
a  light-wagon  against  the  owner  of  a  coach  for  damages  caused 
by  a  collision.     The  complaint  was  that  the  latter  was  driving 
so  fast,  that  when  the  two  carriages  struck,  the  driver  of  the 
former  was  thrown  forward  over  the  dash-board.     Show  how 
his  own  testimony  proved  him  to  have  been  at  fault. 

When  the  light-wagon  was  suddenly  stopped,  its  driver  went 
on  by  his  inertia  with  the  same  speed  at  which  the  wagon  was 
moving.  That  this  threw  him  forward  over  the  dash-board, 
proves  his  speed  to  have  been  unusual. 

10.  Suppose  a  train  moving  at  the  rate  of  '30  miles  per  hour ; 
on  the  rear  platform  is  a  cannon  aimed  parallel  with  the  track 
and  in  a  direction  precisely  opposite  to  the  motion  of  the  car. 
Let  a  ball  be  discharged  with  the  exact  speed  of  the  train, 
where  would  it  fall? 

In  a  vertical  line  to  the  track.  The  two  equal,  opposite 
motions  would  exactly  destroy  each  other. 

11.  Suppose  a  steamer  in  rapid  motion  and  on  its  deck  a 
man  jumping.     Can  he  jump  further  by  leaping  the  way  the 
boat  is  moving  or  in  the  opposite  direction  ? 

It  will  make  no  difference  as  long  as  he  jumps  on  the  deck. 
Should  he  jump  off  the  boat,  then  the  effect  would  be  different. 

12.  Why  is  a  running  jump  longer  than  a  standing  one? 
Because  the  motion  gained  in  running  is  retained  in  the 

jump  and  adds  to  its  distance. 

13.  If  a  stone  be  dropped  from  the  mast-head  of  a  vesselin 
motion,  will  it  strike  the  same  spot  on  the  deck  that  it  would  if 
the  vessel  were  at  rest  ? 

It  will.  It  falls  with  the  motion  of  the  vessel,  and  goes  just 
as  far  forward  while  falling  as  the  vessel  does. 


IN  NATURAL  PHILOSOPHY.  17 

\ 

14.  Could  a  party  play  ball  on  the  deck  of  the  Great  Eastern 
when  steaming  along  at  the  rate  of  20  miles  per  hour,  without 
making  allowance  for  the  motion  of  the  ship? 

They  could.  The  ball  would  have  the  motion  of  the  ship, 
and  would  move  with  it  in  whatever  direction  they  might 
throw  it. 

15.  Since  "action  is  equal  to  reaction,"  why  is  it  not  as  dan- 
gerous to  receive  the  "  kick"  of  a  gun  as  the  force  of  the  bullet? 

The  striking  force  is  as  the  square  of  the  velocity;  and  the 
velocity  with  which  the  gun  moves  backward  is  as  much  less 
than  that  with  which  the  bullet  moves  forward,  as  the  gun  is 
heavier  than  the  bullet.  For  this  reason  a  heavy  gun  will 
kick  much  less  than  a  light  one. 

1 6.  If  you  were  to  jump  from  a  carriage  in  rapid  motion, 
would  you  leap  directly  toward  the  spot  on  which  you  wished 
to  alight? 

No ;  because  as  one  jumps  from  the  wagon  he  has  its  for- 
ward motion,  and  will  go  just  as  far  ahead,  while  leaping,  as 
he  would  if  he  had  remained  in  the  carriage.  He  should, 
therefore,  aim  a  little  back  of  the  desired  alighting-place. 

1.7.  If  you  wished  to  shoot  a  bird  in  swift  flight,  would  you 
aim  directly  at  it  ? 

No.  The  bird  will  fly  forward  while  the  bullet  is  going  to 
it.  One  should,  therefore,  aim  a  little  in  advance. 

1 8.  At  what  parts  of  the  earth  is  the  centrifugal  force  the 
least? 

The  poles.     They  simply  turn  around  in  24  hours. 

19.  What  causes  the  mud  to  fly  from  the  wheels  of  a  carriage 
in  rapid  motion  ? 

The  centrifugal  force. 

20.  What  proof  have  we  that  the  earth  was  once  a  soft  mass  ? 
It  is  flattened  at  the  poles.     This  effect  is  produced  upon  a 

ball  of  soft  clay  by  simply  revolving  it  on  a  wire  axis. 

21.  On  a  curve  in   a   railroad,  why  is  one  track  always 
higher  than  the  other? 


1 8  ANSWERS  TO  PRACTICAL  QUESTIONS 

The  outer  track  is  raised  that  gravity  may  balance  the  cen- 
trifugal force. 

22.  What  is  the  principle  of  the  sling  f 

The  sling  is  whirled  until  a  strong  centrifugal  force  is 
generated ;  the  string,  the  centripetal  force,  is  then  released, 
when  the  stone  flies  off  at  a  tangent. 

23.  The  mouth  of  the  Mississippi  river  is  about  T.\  miles 
further  from  the  centre  of  the  earth  than  its  source.      What 
causes  its  water  to  thus  "run  up  hill?" 

The  centrifugal  force  produced  by  the  revolution  of  the  earth 
on  its  axis  tends  to  drive  the  water  from  the  poles  toward  the 
equator.  Were  the  earth  to  stand  still  in  its  daily  rotation,  the 
Gulf  of  Mexico  would  empty  its  waters  back  through  the  Mis- 
sissippi to  the  northern  regions. 

24.  Is  it  action  or  reaction  that  breaks  an  egg  when  I  strike 
it  against  the  table  f 

The  reaction  of  the  table. 

25.  Was  the  man  philosophical  who  said  ll  it  was  not  thr 
falling  so  far  but  the  stopping  so  quick  that  hurt  him  f" 

He  was. 

26.  If  one  person  runs  against  another,  which  receives  the 
greater  blow  f 

Action  is  equal  to  reaction :  hence  the  blows  must  be  equal. 

27.  Would  it  vary  the  effect  if  the  two  persons  were  running 
in  opposite  directions  ? 

The  blow  would  then  be  the  sum  of  both  their  momenta. 

If  they  were  running  in  the  same  direction  ? 

The  blow  would  be  equal  to  the  difference  of  their  momenta. 

28.  Why  can  you  not  fire  a  rifle-ball  around  a  hill?  • 
Because  a  single  force  always  produces  motion  in  a  straight 

line. 

29.  Why  does  a  heavy  gun  "  kicK"  less  than  a  light  one? 
See  problem  15. 

30.  A  man  on  the  deck  of  a  large  steamer  draws  a  small 


IN  NATUBAL  PHILOSOPHY.  19 

boat  toward  him.     How  much  does  the  ship  move  to  meet  tht 
boat? 

The  ship  moves  as  much  less  distance  than  the  boat,  as  it  is 
heavier  than  the  boat. 

31.  Suppose  a  string,  fastened  at  one  end,  will  just  support 
a  weight  of  '25  Ibs.  at  the  other.     Unfasten  it,  and  let  two  per- 
sons pull  ripon  it  in  opposite  directions.     How  much  can  each 
pull  without  breaking  it  ? 

25  Ibs.  The  second  person,  in  the  latter  case,  can  pull  as 
much  as  the  nail  did  in  the  former. 

32.  Can  a  man  standing  on  a  platform-scale  make  himself 
lighter  by  lifting  up  on  himself? 

He  cannot ;  because  action  is  equal  to  reaction,  and  in  an 
opposite  direction.  As  much  as  he  lifts  up,  so  much  must  he 
press  down. 

33.  Why  cannot  a  man  lift  himself  by  pulling  up  on  hi\ 
boot-straps  f 

See  last  problem. 

34.  If  from  a  gun  placed  vertically,  a  ball  were  Jired  into 
perfectly  still  air,  where  would  it  fall? 

It  would  return  into  the  gun. 

35.  With  what  momentum   would  a  steamboat  weighing 
1,000  tons,  and  moving  with  a  velocity  of  10  feet  per  second, 
strike  against  a.  sunken  rock  f 

1000  tons  x  10a  =  100,000  tons. 

36.  With  what  momentum  would  a  train  of  cars  weighing 
loo  tons,  and  running  10  miles  per  hour,  strike  against  an 
obstacle? 

The  velocity  per  second  is  142/3  ft.    100  tons  x  (14V,)'  =  21,511%  tons. 

37.  What  would  be  the  comparative  striking-force  of  two 
hammers,  one  driven  with  a  velocity  of  '20  feet  per  second,  ana 
the  other  lofeet? 

202  =  400.  102  =  100.  400  : 100 . :  1 :  4.  Hence  one  will  strike  four  times  as 
hard  a  blow  as  the  other.  This  principle  is  of  great  importance  in  chopping 
wood,  splitting  rails,  and  in  all  cases  where  percussion  is  concerned.  The 
highest  attainable  velocity  is  to  be  sought. 


2O  AM8WERS  TO  PRACTICAL    QUESTIONS 

— There  is  a  story  told  of  a  man  who  erected  a  huge  pair  of 
bellows  in  the  stern  of  his  pleasure-boat,  that  he  might  always 
have  a  fair  wind.  On  trial  the  plan  failed.  In  which  di- 
rection should  he  have  turned  the  bellows  f 

In  the  manner  adopted  at  first,  of  turning  the  nozzle  toward 
ihe  sails,  the  action  of  the  wind  against  the  sails  and  the  re- 
action of  the  bellows  against  the  boat  just  balanced  each  other. 
If  the  man  had  turned  the  nozzle  backward  he  could  have 
saved  the  reaction  of  the  bellows  to  move  the  boat.  This 
would,  however,  have  been  a  most  costly  and  bungling  way 
of  navigation. 

— If  we  whirl  a  pail  of  water  swiftly  around  with  our  hand, 
why  will  the  water  all  tend  to  leave  the  centre  of  the  pail  ? 
Why  will  the  foam  all  collect  in  the  hollow  at  the  centre  ? 


THE  MECHANICAL  POWERS. 

90.  i.  Describe  the  rudder  of  a  boat  as  a  lever. 

The  water  is  the  F,  the  boat  the  W,  and  the  hand  the  P. 
As  the  W  is  between  the  F  and  the  P,  it  is  a  lever  of  the 
second  class. 

2.  Show  the  change  that  occurs  from  the  second  to  the  third 
class  of  levers,  when  you  take  hold  of  a  ladder  at  one  end  and 
raise  it  against  a  building. 

At  first  the  ground  is  the  F  at  one  end,  the  hand  the  P  at 
the  other,  and  the  ladder  the  W  hanging  between ;  hence  this 
is  a  lever  of  the  second  class.  After  a  little,  the  F  remaining 
the  same,  the  P  is  applied  at  one  end,  near  the  F,  and  the 
ladder  is  the  W  hanging  at  the  other ;  hence  this  is  now  a 
lever  of  the  third  class. 

3.  Why   is  a  pinch  from  the  tongs  near  the  hinge  more 
severe  than  one  near  the  end  f 

Because  in  the  former  case  the  tongs  are  a  lever  of  the  first 
class — in  the  latter,  of  the  third.  In  the  first  class  there  is  a 
gain  of  power,  in  the  third  a  loss. 

4.  Two  persons  are  carrying  a  weight  0/250  Ibs.,  hanging 


IN  NA  TURAL  PHIL OSOPHT.  2  I 

between  them  from  a  pole  10  feet  in  length.      Where  should  it 
be  suspended  so  that  one  will  lift  only  50  Ibs.  ? 

One  lifts  50  Ibs. ;  the  other  200  Ibs.  The  proportionate  length  of  the  arms 
of  the  lever  should  be  the  same  as  the  proportionate  weights— i. «.,  1  to  4. 
10  •*•  5  =  2,  the  unit  of  measure.  Hence  one  arm  is  2  feet  long  and  the  other 
8  feet  long.  PROOF.— (See  Prob.  7,  p.  10.)  50  x  8  =  200  x  2.  This  is  the 
Bubstance  also  of  the  equation  P  x  Pd  =  W  x  Wd. 

5.  In  a  lever  of  the  first  class,  6  feet  long,  where  should  tht 
F  be  placed  so  that  a  P  of  \  Ib.  will  balance  a  W  of  2.3  Ibs.  f 

6  feet  =  72  inches.  72  -*-  24  =  3,  the  unit  of  distance.  The  W  must  be 
placed  3  in.  and  the  P  69  in.  from  the  F.  PROOF.  23  x  3  =  1  x  69  (Prob.  4). 

6.  What  P  would  be  required  to  lift  a  barrel  of  pork  with  a 
windlass  whose  axle  is  one  foot  in  diameter  and  handle  3  ft. 

long? 

P  :  W  :  rad.  of  axle  : :  rad.  of  wheol. 

a;  :  200  Ibs  : :  Va  ft.  :  3  ft. 
x  =  33Vs  Ibs. 

7.  What  sized  axle,  with  a  wheel  6  feet  in  diameter,  would 
be  required  to  balance  a  W  of  i  ton  by  a  P  of  100  Ibs.  f 

P  :  W  : :  rad.  of  axle  :  rad.  of  wheel. 

100  Ibs.  :  2000  Ibs.  : :  x  :  3  ft. 
x  =  '/ao  ft-  =  the  r&d- ;  hence  the  diameter  =  8/io  ft- 

8.  What  number  of  movable  pulleys  would  be  required  to 
lift  a  W  of  200  Ibs.  with  a  P  of  2$  Ibs.  ? 

TTT 

W—  P  x  twice  the  no.  of  mov.  pulleys ;  hence  — =  twice  the  no.  of  mov.  pul's. 
200  •+•  25  =  8.    8  -*-  2  =  4  =  the  no.  required. 

9.  How  many  Ibs.  could  be  lifted  with  a  system  of  '4  movable 
pulleys,  and  one  fixed  pulley  to  change  the  direction  of  the 
force,  by  a  P  of  100  Ibs.  ? 

W=  P  x  twice  the  no.  of  mov.  pulleys. 
100  Ibs.  x  (4  x  2)  =  800  Ibs.  =  the  W. 

10.  What  weight  could  be  lifted  with  a  single  horse-power 
^33,000  Ibs.)  acting  on  the  tackle-block?    (Fig.  62.) 

This  block  has  3  movable  pulleys,  and  using  the  equation  of  the  pulleys  given 
in  the  last  two  problems,  we  have,  making  no  allowance  for  friction, 

33,000  Ibs.  x  (3x2)  =  198,000  Ibs. 


22  ANSWERS   TO  PRACTICAL   QUESTIONS 

1 1.  What  distance  should  there  be  between  the  threads  of  a 
screw,  that  a  Po/2$  Ids.,  acting  on  a  handle  3  //.  long,  may 
lift  i  ton  weight? 

F  :  W  : :  Interval  :  Circumference. 

25  Ibs.  :  2000  Ibs.  : :  x  :  72  in.  x  3.1416. 

x  =  2.83  -in. 

12.  How  high  could  a  P  of  11  Ibs.,  moving  i6//.  along  an 
inclined  plane,  lift  a  W 'of '96  Ibs.? 

P  :  W  : :  height  :  length. 

12  Ibs  :  96  Ibs.  :  :  x  :  16  ft. 

x  =  2  ft. 

13.  /  wish  to  roll  a  barrel  of  flour  into  a  wagon,  the  box  of 
which  is  4//.  from  the  ground.     I  can  lift  but  24  Ibs.     How 
long  a  plank  should  I  get? 

P  :  W  : :  height  :  length. 
24  Ibs  :  196  Ibs.  : :  4  ft.  :  x  =  322/3  ft. 

14.  The  "  evener"  of  a  pair  of  whiffletrees  is  ^ft.  6  in.  long  , 
how  much  must  the  whiffletree  be  moved  to  give  one  horse  the 
advantage  of  \  over  the  other  ? 

For  every  3  Ibs.  one  horse  pulls,  the  other  must  pull  4  Ibs. :  hence  7  represents 
the  proportion  in  which  the  load  is  to  be  divided.  3  ft.  6  in.  =  42  inches.  42 
in.  -*-7  =  6  inches,  the  unit  of  measure.  Hence  one  arm  of  the  evener  must  be 
6  in.  x  3  =  18  in.  long,  and  the  other  6  in.  x  4  =  24  in.  long.  Or,  if  we  prefer,  we 
may  say  21  in.  —  3  in.  =  18  in.  Ions:,  and  21  in.  +  3  in.  =  24  in.  long.  PROOF.- 
(See  Prob.  4,  p.  20.)  18  x  4  =  24  x  3  =  72. 

15.  In  a  set  of  three  horse  whiffletrees,  having  an  "  evene-r" 
5//.  long,  at  what  point  should  the  plough-clevis  be  attached 
that  the  single  horse  may  draw  the  same  as  each  one  of  the 
span  of  horses  ? 

For  every  Ib.  drawn  by  the  single  horse  the  span  should  draw  2  Ibs. :  hence 
3  represents  the  proportion  in  which  the  load  is  to  be  divided.  60  hi.  •+•  3  =  20 
in.,  the  unit  of  measure.  20  in.  x  1  =  20  in.,  and  20  in.  x  2  =  40  in.  Hence  eno 
arm  mast  be  20  in.,  and  the  other  40  in.  long. 

To  give  \  advantage  ? 

The  single  horse  should  draw  3  Ibs.  and  each  of  the  others  4  Ibs. :  hence  the 
span  should  draw  8  Ibs.  60  in.  •+- 11  =  56/n  in.,  the  unit  of  measure.  5»/n  in. 
x  3  =  16«/ii  in.,  and  56/u  in.  x  8  =  437/n  in. 

1 6.  What  W  can  be  lifted  with  a  P  of  100  Ibs.  acting  en  a 
screw  having  threads  \  of  an  inch  apart  and  a  lever  handle  4 
//.  long? 


72V  NATURAL  PHILOSOPHY.  2) 

P  :  W  : :  Interval  :  Circumference. 
100  Ibs.  :  x  : :  »/4  in.  :  96  in.  x  3.1416. 
x  =  120,637  -fibs. 

17.  What  is  the  object  of  the  big  balls  cast  on  the  ends  of  tht 
handle  of  the  screw  used  in  copying-presses  ? 

By  their  inertia  and  centrifugal  force  they  make  the  motion 
more  uniform  and  continuous. 

1 8.  In  a  steelyard  7.  ft.  long,  the  distance  from  the  'weight- 
hook  to  the  fulcrum-hook  is  i  in.     How  heavy  a  body  can  be 
•weighed  with  a  I  Ib.  weight  at  the  further  end  ? 

84  in.—  2  in.  =  22  in.    1  Ib.  x  22  =  22  Ibs.  =  P.    22  Ibs.  •+- 2  =  11  Ibs.  =  W. 

19.  Describe  the  change  from  the  \st  to  the  ^d  class  of  levers, 
in  the  different  ways  of  using  a  spade. 

When  digging,  the  ground  at  the  back  of  the  spade  is  the 
F  ;  the  ground  lifted  is  the  W  ;  and  the  hand  at  the  other  end 
is  the  P.  As  the  W  is  at  one  end,  P  at  the  other,  and  the  F 
between,  this  is  a  lever  of  the  ist  class.  When  throwing 
dirt,  the  left  hand  at  one  end  of  the  spade  is  the  F ;  the  dirt 
at  the  other  end  is  the  W,  and  the  right  hand  between  the 
two  is  the  P.  As  the  P  is  between  the  F  and  the  W,  this  is  a 
lever  of  the  3d  class. 

20.  Why  are  not  blacksmiths'  and  fire  tongs  constructed  on 
the  same  principle  ? 

The  former  are  of  the  ist  class,  as  power  is  required:  the 
latter  of  the  3d  class,  as  rapidity  only  is  necessary. 

21.  In  a  lever  of  the  $d  class,  what  W  will  a  P  of  50  Ibs. 
balance,  if  one  arm  is  12  ft.  and  the  other  3  ft.  long? 

P  :  W  : :  Wd  :  Pd . 

50  Ibs.  :  x  : :  12  ft.  :  3  ft. 
x  =  12Va  Ibs. 

22.  In  a  lever  of  the  id  class,  what  W  will  a  P  of  50  Ibs. 
balance,  with  a  lever  12  feet  long  and  W  ^  feet  from  the  Ff 

50  lb«.  :  x  : :  3  ft.  :  12  ft. 

x  =  200  Ibs. 


24  ANSWERS  TO  PRACTICAL   QUESTIONS 

23.  In  a  lever  of  the  ist  class ;  what  IV  will  a  P  of  50  Ibs 
balance,  with  a  lever  12  ft.  long  and  the  F '3  ft.  from  the  IV? 

50  Ibs.  :  x  : :  3  ft.  :  9  ft. 
x  =  150  Ibs. 

24.  In  a  wheel  and  axle,  the  P=^o  Ibs.,  ^=360  Ibs., 
diameter  of  axle  =  8  in.     Required  the  circumference  of  thi 
•wheel. 

P  :  W  ::  diameter  of  axle  :  diam.  of  wheel 

40  Ibs.  :  360  Ibs.  : :  8  in.  :  x  -  72  in.  =  6  ft.,  the  diameter  of  wheel. 
6  ft.  x  3.1416  =  18.85  ft.,  the  circumference  of  the  wheel. 

25.  In  a  wheel  and  axle  the  P  =-20  Ibs.,  the  ^=240  Its., 
and  the  diameter  of  wheel  =  \ft.     Required  the  circumference, 
of  the  axle. 

20  Ibs  :  240  Ibs  ::  a? :  48  in. 

X  =  4  in.  (diameter  of  axle). 

4  in.  x  3.1416  =  12.56  in.  (circumference). 

26.  Required,  in  a  wheel  and  axle,  the  diameter  of  the  wheel, 
the  diameter  of  the  axle  being  10  inches,  P  =  100  Ibs.  and  W 
—  I  ton. 

100  Ibs.  :  2000  Ibs.  : :  10  in.  :  x  =  200  in.  =  16a/s  ft. 

27.  What  P  would  be  necessary  to  sustain  a  weight  oj 
3,780  Ibs.,  with  a  system  of  6  movable  pulleys  and  one  ropef 

W  =  P  x  twice  the  no.  of  mov.  pulleys. 
3,780  Ibs.  =  P  x  (6  x  2).    P  =  315  Ibs. 

28.  How  many  movable  pulleys  would  be  required  to  sustain 
i  W 0/420  Ibs.  with  a  P  of  210  Ibs.  f — Ans.   I. 


HYDROSTATICS. 

121.  i.  Why  do  housekeepers  test  the  strength  of  lye,  by 
trying  whether  or  not  an  egg  will  float  on  it  ? 

The  potash  dissolved  in  the  water  to  form  lye  increases  the 
density  of  the  liquid.  When  enough  has  been  dissolved  to 
make  its  specific  gravity  greater  than  that  of  the  egg,  the  egg 
will  float.  This  becomes,  therefore,  a  simple  means  of  testing 
the  amount  of  potash  contained  in  the  lye. 


/A  AATUHAL  PHILOSOPHY.  25 

'2.  How  muck  wafer  will  it  take  to  make  a  gallon  of  strong 
brine  ? 

A  gallon.     The  salt  does  not  increase  the  bulk  of  the  liquid. 

3.  Why  can  a  fat  man  swim  easier  than  a  lean  one  ? 
Because  muscles  and  bones  are  heavier  than  fat.    The  speci- 
fic gravity  of  a  fat  man  is  therefore  less  than  that  of  a  lean  one. 

4.  Why  does  the  firing  of  a  cannon  over  the  water  sometimes 
bring  to  the  surface  the  body  of  a  drowned  person  ? 

One  answer  is  given  in  the  Philosophy.  It  is  probable,  also, 
that  the  firing  of  the  gun  produces  a  partial  vacuum,  or  in 
some  way  takes  off,  for  an  instant,  a  part  of  the  pressure  of  the 
air  on  the  water.  The  gases  in  the  body  would  then  expand 
and  bring  it  to  the  top. 

6.  If  we  let  bubbles  of  air  pass  up  through  a  jar  of  water, 
why  will  they  become  larger  as  they  ascend? 

The  pressure  of  the  water  is  less  as  they  near  the  top,  and 
so  they  expand. 

7.  What  is  the  pressure  on  a  lock-gate  14  feet  high  and  10 
feet  wide,  when  the  lock  is  full  of  water  ? 

14  x  10  x  7  x  1000  oz.  =  980,000  oz.  =  61,250  Ibs. 

5.  Will  a  pail  of  water  weigh  any  more  with  a  live  Jish  in 
it  than  without  ? 

If  the  pail  were  full  before  the  fish  was  put  in,  then  it  will 
make  no  difference,  since  the  fish  will  displace  its  own  weight 
of  water,  which  will  run  over.  If  the  pail  is  only  partially 
filled,  then,  though  the  fish  is  upheld  by  the  buoyancy  of  the 
water,  since  action  is  equal  to  reaction,  it  adds  its  own  weight 
to  that  of  the  water. 

— If  a  man  and  a  boy  were  riding  in  a  wagon,  and,  on  com- 
ing to  the  foot  of  a  hill,  the  man  should  take  up  the  boy  in  his 
arms,  would  not  that  help  the  horse? 

9.  If  the  water  filtering  down  through  a  rock  should  collect 
in  a  crevice  an  inch  square  and  250  feet  high,  opening  at  the 
bottom  into  a  closed  fissure  having  20  square  feet  of  surface, 
•whut  would  be  the  total  pressure  tending  to  break  the  rock  ? 

2 


26  ANSWERS  TO  PRACTICAL   QUESTIONS 

The  pressure  is  proportional  to  the  height  and  not  the  size  of  the  column, 
hence  the  pressure  ia 

20  x  250  x  1000  oz.  =  5,000,000  oz.  =  312,500  Ibs. 

10.  Why  can  stones  in  water  be  moved  so  imtch  mort  easily 
than  on  land? 

Because  the  water  buoys  up  about  one-half  of  their  weight. 

11.  Why  is  it  so  difficult  to  wade  in  the  water  where  there 
is  any  current? 

Because  the  buoyant  force  of  the  water  makes  us  so  light 
that  we  are  easily  carried  away  from  our  footing. 

12.  Why  is  a  mill-dam  or  a  canal  embankment  small  at  the. 
top  and  large  at  the  bottom  ? 

Because  the  pressure  of  the  water  increases  with  the  depth. 

13.  In  digging  canals  and  building  railroads,  oiight  not  the 
engineer  to  take  into  consideration  the  curvature  of  the  earth  ? 

Certainly.  If  he  should  build  on  a  true  level  he  would  find 
his  embankment  pointing  up  to  the  stars. 

14.  Is  the  water  at  the  bottom  of  the  ocean  denser  than  that 
at  the  surface  f 

The  immense  pressure  must  condense  it  very  much  at  great 
depths.  There  is  a  certain  point  beyond  which  divers  cannot 
penetrate. 

15.  Why  does  the  bubble  of  air  in  a  spirit-level  move  as  the 
instrument  is  turned? 

Because  the  air  is  lighter  than  the  alcohol  and  rises  con- 
stantly to  the  highest  point.  For  this  reason,  also,  the  tube 
is  curved  upward  at  the  centre. 

1 6.  Why  can  a  swimmer  tread  on  glass  and  other  sharp 
substances  at  the  bottom  of  the  water  with  little  harm  ? 

See  problem  11. 

1 7.  Will  a  vessel  draw  more  water  in  salt  or  in  fresh  water  f 
In  fresh,  because  its  specific  gravity  is  less. 

1 8.  Will  iron  sink  in  mercury  ? 

No.     It  will  float,  like  a  cork  on  water. 

19.  The  water  in  the  reservoir  in  New  York  is  about  80  feel 


IN  NA  TOR  A  L  PHIL  OSOPHT.  2  J 

above  the  fountain  in  the  City  Hall  Park.      What  is  the  pres- 
sure on  a  single  hick  of  the  pipe  at  the  latter  point  f 

(1000  oz.  x  80)  •*•  144  =  34.7  Ibs. 

20.  Why  does  cream  rise  on  milk  ? 
Because  it  is  lighter  than  the  milk. 

21.  If  a  skip  founders  at  sea,  to  what  depth  will  it  sink  ? 
Until  its  specific  gravity  becomes  equal  to  that  of  the  water  ? 

22.  There  is  a  story  told  of  a  Chinese  boy  who  accidentally 
dropped  his  ball  into  a  deep  hole,  where  he  ctfuld  not  reach  it. 
He  filled  the  hole  with  water,  but  the  ball  would  not  quite  float. 
He  finally  bethought  himself  of  a  lucky  expedient,  which  was 
successful.     Can  you  guess  it  ? 

He  put  salt  in  the  water. 

23.  Which  has  the  greater  buoyant  force,  oil  or  water? 
Water,  because  its  density  is  greater. 

24.  What  is  the  weight  of  '4  cu.  ft.  of  cork  ? 

1000  oz.  =  the  weight  of  1  en.  ft.  of  water 

.240  =  the  spec.  grav.  of  cork. 
240  oz.  =  the  weight  of  1  cu.  ft.  of  cork. 
4 


25.  How  many  oz.  of  iron  will  a  cubic  foot  of  cork  float  in 

water  ? 

1000  oz.  =  weight  of  a  cubic  foot  of  water. 
.240       =  ppoc.  grav.  of  cork. 

240        =  weight  of  a  cubic  foot  of  cork. 
1000  oz.  —  240  oz.  =  760  oz.,  the  buoyant  force  of  a  cubic  foot. 

26.  What  is  the  specific  gravity  of  a  body  whose  weight  in 
air  is  30  grs.  and  in  water  20  grs.  ? 

30  grs.  —  20  grs.  =  10  grs. 

30  grs. -«- 10  grs.  =  3. 
The  body  is  three  times  as  heavy  as  water. 

27.  Which  is  heavier,  a  pail  of  fresh  water  or  one  of  salt- 
water? 

A  pail  of  salt-water  is  as  much  heavier  than  one  of  fresh- 
water as  the  weight  of  the  salt  added  to  make  the  brine. 


28  ANSWERS  TO  PRACTICAL 

28.  The  weights  of  a  piece  of  syenite -rock  in  air  and  tn 
water  were  3941.8  grs.  and  2607. 5  grs.     Find  its  spec.  grav. 

•  -Ans.  2.954. 

29.  A  specimen  of  green  sapphire  from  Siam  weighed  in 
02>  21.45  grs.,  and  in  water  16.33  Srs-     Required  its  spec, 
grav. — Ans.  4.189. 

30.  A  specimen  of  granite  weighs  in  air  534.8  grs.,  and  tn 
water  334.6  grs.      What  is  the  spec.  grav.  ? — Ans.   2.671. 

3 1 .  What  is  the  bulk  of  a  ton  of  iron  ? 

1000   oz.  =  weight  of  1  en.  ft.  of  water. 
7.8        =  spec.  grav.  of  iron. 


7800  oz.  =  weight  of  a  cu.  ft.  of  iron. 
82,000  oz.  (a  ton  of  iron)  -H  7,800  (weight  of  a  cu.  ft.)  =  44/»» 

A  ton  of  gold? 

1,000  oz.  =  weight  of  a  cu.  ft.  of  water. 
19.34  =  spec.  grav.  of  gold. 

19,340  oz.*  =  weight  of  a  cu.  ft.  of  gold. 
32,000  oz.*  -H  19,340  oz.  =  1.6,  the  no.  of  cu.  ft. 

A  ton  of  copper? 

1000  oz.  x  8.9  =  8900  oz. 
32,000  oz.  -*•  8900  oz.  =  3.6  (nearly)  the  no.  of  cu.  ft. 

32.  What  is  the  weight  of  a  cube  of  gold  4  feet  on  each 

side  ? 

43  =  64,  the  no.  of  cu.  ft. 
19,340  oz.*  (no.  of  oz.  in  1  cu.  ft.)  x  64  =  77,360  Ibs. 

33.  A  cistern  is  12  ft.  long,  6ft.   wide,  and  10  ft.   deep 
When  full  of  water,  what  is  the  pressure  on  each  side  ? 

On  one  side,  12  x  10  x  5  x  1000  oz.  =  600,000  oz.  =  37,500  Ibs. 
On  one  end,    6  x  10  x  5  x  1000  oz.  =  300,000  oz.  =  18.750  Ibs. 

34.  Why  does  a  dead  fish  always  float  on  its  back  ? 

It  has  its  swimming  bladder  located  just  under  the  spine; 
and  this  is  the  lightest  part  of  its  body,  and,  of  course,  comes 
to  the  top  as  soon  as  the  fish  dies. 

*  In  these  solutions  the  student  should  notice  that  avoirdupois  weight  is  used 
in  weighing  the  gol.l.  To  be  exact,  1,000  oz.,  the  weight  of  a  cu.  ft.  of  water, 
should  be  reduced  to  Troy  weight,  and  the  Ib.  gold  taken  as  12  oz.  Troy,  when 
the  ans.  would  be  about  1.36  cu.  ft. 


IN  NATURAL  PHILOSOPHY.  29 

36.  A  vessel  holds  10  Ibs.  of  water:    how   much  n.trcury 
•would  it  contain  ? 

Mercury  is  13.5  times  heavier  than  water.    Hence  the  vessel  would  contain 
10  Ibs.  x  13.5  =  135  Ibs.  of  mercury. 

37.  A  stone  weighs  70  Ibs.  in  air  and  50  in  water.      What 
is  its  bulk  ? 

70  —  50  =  20.    20  x  15  oz.  =  320  oz.,  the  weight  of  water  displaced. 
320  oz.  is  %£  of  a  cu.  ft. 

38.  A  hollow  ball  of  iron  weighs  10  Ibs.  :  what  must  be  its 
bulk,  to  float  in  water? 

10  Ibs.  =  160  oz.    As  a  cubic  ft.  of  water  weighs  1,000  oz.,  the  ball  must  dis- 
place such  a  part  of  a  ca.  ft.  of  water  as  1,000  oz.  is  contained  times  in  160  oz 
which  is  .16  en.  ft. 


HYDRAULICS. 

521.  i.  How  much  more  water  can  be  drawn  from  a  faucet 
,  than  from  one  4  feet  below  the  surface  of  the  water  in  a 
cistern  ? 

y  =  2  Vffd ;  hence  v  =  2  V716  x  8  =  2S.6. 
v  =  2  N/16x4  =  16. 

Hence  6.6  cu.  ft.  more  would  flow  from  one  than  from  the 
other  in  each  second. 

•2.  How  much  water  would  be  discharged  per  second  from 
a  short  pipe  having  a  diameter  of  4  inches  and  a  depth  of  48 
feet  below  the  surface  of  the  water  ? 

42=16.    IP.  x  .7854=12.57  sq.  inches=.087  sq.  ft.  (area  of  the  tube). 

v  =  &Sgd  =  2^16^48  =  55.4 

.087  x  55.4  =  4.8  cu.  ft. 

3.  When  we  pour  molasses  frojn  a  jug,  why  is  the  stream  so 
much  larger  near  the  nozzle  than  at  some  distance  from  it? 

Because,  according  to  the  law  of  falling  bodies,  the  further 
the  molasses  falls  the  faster  it  falls.  The  stream,  therefore, 
becomes  smaller  as  it  moves  more  swiftly,  until,  at  last,  it 
breaks  up  into  drops. 


3O  ANSWERS  TO  PRACTICAL   QUESTIONS 

4.  Ought  a  faucet  to  extend  into  a  barrel  beyona  the  staves  * 
No ;  because  cross  currents  would  be  produced,  which  would 

interfere  with  the  free  passage  of  the  liquid. 

5.  What  would  be  the  effect  if  both  the  openings  in  one  of 
the  arms  in  Barker's  Mill  were  on  the  same  side  ? 

It  would  cease  revolving.  The  pressure  in  each  direction 
would  then  be  equal,  and  the  arms  would  balance. 

PNEUMATICS. 

14§.  i.  Why  must  we  make  two  openings  in  a  barrel  of 
fider  when  we  tap  it  ? 

One  to  let  out  the  cider,  and  one  to  admit  the  air. 

2.  What  is  the  weight  of  10  cubic  feet  of  air? 

100  cu.  in.  weigh  31  grs». ;  hence  10  cu.  ft.  will  weigh  31  grs.  x  172.8  =  .7652 
Ibs.  avoirdupois. 

3.  What  is  the  pressure  of  the  air  on  one  square  rod  of  land? 

272»/4  x  144  x  15  Ibs.  =  588,060  Ibs. 

4.  What  is  the  pressure  on   a  pair  of  Magdeburg  hemispheres 
4  in.  in  diameter,  when  the  air  is  entirely  exhausted  ? 

3.1416  x  4a  x  15  IbP.  =  753.9  Ibs. 

5.  How  high  a  column  of  water  can  the  air  sustain  when 
the  barometric  column  stands  at  28  in.  ? 

28  in.  x  l3'/a  =  31  Vu  feet. 

6.  If  we  should  add  a  pressure  of  two  atmospheres,  what 
would  be  the  bulk  of  100  cu.  in.  of  common  air? 

The  pressure  is  trebled,  and  according  to  Mariotte's  law,  the  volume  will 
be  reduced  in  the  same  proportion  ;  hence  it  will  be  100  cu.  in.  -s-  3  =  331/? 
cu.  in. 

7.  If,  while  the  water  is  running  through  the  siphon,  we 
quickly  lift  the  long  arm,  what  will  be  the. effect  on  the  water  in 
the  siphon  ? 

It  will  all  run  back  through  the  short  arm  into  the  vessel. 

8.  If  we  lift  the  entire  siphon  f 

The  water  will  all  run  out  the  long  arm.     The  reason  of  this 


IN  NATURAL  PHILOSOPHY.  31 

difference  is,  that  when  we  lift  the  long  arm  we  make  it  in 
effect  the  short  arm,  and  the  other  arm  the  long  one. 

8.  When  the  mercury  stands  at  29^  in.  in  the  barometer, 
how  high  above  the  surface  of  the  water  can  we  place  the  lower 
pump-valve  ? 

In  theory,  29^  in.  X  13^  =  398^  in.;  in  practice,  the  distance 
is  much  less  than  this. 

9.  Why  cannot  we  raise  water,  by  means  of  a  siphon,  to 
a  higher  level? 

There  is  no  power  in  a  siphon  ;  it  is  only  a  way  of  guiding 
the  flow  of  water  to  a  lower  level. 

10.  If  the  air  in  the  chamber  of  a  fire-engine  be  condensed 
to  fe  its  former  bulk,  what  will  be  the  pressure  due  to  the  ex- 
pansive force  of  the  air  on  every  square  inch  ? — Ans.  240  Ibs. 

1 1 .  What  causes  the  bubbles  to  rise  to  the  surface,  when  we 
put  a  lump  of  loaf-sugar  in  hot  tea  ? 

The  bubbles  of  air  contained  in  the  pores  of  the  sugar  rise 
because  they  are  lighter  than  the  water. 

12.  To  what  height  can  a  balloon  ascend? 

Until  its  specific  gravity  is  the  same  as  that  of  the  air  in 
which  it  floats. 

—  What  weight  can  it  lift? 

A  weight  equal  to  the  difference  between  its  own  weight  and 
that  of  the  air  it  displaces. 

13.  Why  is  the  air  lighter  in  foul  and  heavier  in  fair 
weather  ? 

This  question  is  answered  in  the  Philosophy.  Another 
reason  may  be,  that  the  upward  currents  of  air  partly  remove 
the  pressure  in  foul  weather. 

14.  When  smoke  ascends  in  a  straight  line,  is  it  a  proof  of 
the  rarity  or  density  of  the  air? 

Of  its  density,  because  it  shows  that  the  smoke  is  much 
lighter  than  the  air,  and  so  rises  immediately  to  the  top. 

it,.  Why  do  we  not  feel  the  heavy  pressure  of  the  air  on  out 
bodies? 


32  ANSWERS  TO  PRACTICAL    QUESTIONS 

Because  it  is  equally  distributed  within  and  without  our 
bodies.  The  pressure  on  a  person  of  ordinary  size  is  about  16 
tons. 

1 6.  Is  a  bottle  empty  when  filled  with  air? 
No ;  because  we  must  empty  the  air  out  before  we  can  fill 
the  bottle  with  anything  else. 

1 8.  How  does  the  variation  in  the  pressiire  of  the  air  affect 
those  who  ascend  lofty  mountains? 

The  outward  pressure  is  there  partly  removed,  and  the 
inner  pressure  remaining  the  same,  the  blood  is  often  forced 
through  the  ears,  nostrils,  etc.  When  one  descends  into  a 
deep  mine  the  conditions  are  reversed :  the  outer  pressure  be- 
comes in  excess  of  the  inner;  severe  pain  is  felt  in  the  ear- 
drum, and  ringing  noises  in  the  head  become  almost  intoler- 
able. These,  however,  disappear  after  a  time,  where  the 
equilibrium  between  the  internal  and  external  pressure  is 
restored.  It  is  said  that  Humboldt  ascended  where  the  mer- 
curial column  fell  to  14  inches,  and  descended  in  a  diving-bell 
where  it  rose  to  45  inches — thus  making  a  variation  of  3 1  inches, 
or  a  difference  of  31,000  Ibs.  pressure  on  his  body. 

— If  the  atmosphere  in  a  diving-bell  were  of  the  same  density 
as  that  at  the  surface  of  the  earth,  how  deep  in  the  water 
would  it  be  necessary  to  sink  the  bell  in  order  to  reduce  the 
volume  of  the  air  one-half,  or,  hi  other  words,  for  the  bell  to 
half  fill  with  water? — Ans.  34  feet. 

How  'near  would  the  bell  be  filled  at  a  depth  of  1,020 
feet. — Ans.  29/3o. 

If  the  bell  were  then  raised,  would  the  water  stay  in  till  it 
reached  the  siirface  f 

The  elasticity  of  the  air  would  cause  it  to  gradually  expand 
and  drive  out  the  water  as  it  rose. 

ACOUSTICS. 

1§4.  i.  Why  cannot  the  rear  of  a  long  column  of  soldiers 
keep  time  fo  the  music  ? 


TN  NA  TURAL  PHIL  OSOPHY. '  3  3 

Because  it  takes  time  for  the  sound-wave  to  pass  down  the 
column,  and  hence  those  in  the  rear  do  not  hear  the  music  as 
soon  as  those  in  front. 

2.  Three  minutes  elapse  between  the  flash  and  the  report  of  a 
thunderbolt :  how  far  distant  is  it  ? 

If  the  air  is  at  the  freezing  point,  the,  distance  is 
1090  ft.  x  60  x  3  =  196,200  ft. 

3.  Five  seconds  expire  between  the  flash  and  report  of  a  gun  : 
what  is  the  distance  ? 

1090ft.x5  =  5450ft 

4.  Suppose  a  speaking-tube  should  connect  two  villages  10 
miles  apart.     How  long  would  it  take  a  sound  to  pass  that 
distance  ? 

52,800  ft.  -f- 1090  ft.  =  48.4  (sec.) 

5.  The  report  of  a  pistol-shot  was  returned  to  the  ear  from 
the  face  of  a  cliff  in  4  seconds.     How  far  was  it? 

1090  ft.  x  a  =  2180  ft. 

6.  What  is  the  cause  of  the  difference  in  the  voice  of  man 
and  woman  ? 

It  may  be  a  difference  in  the  length  of  the  vocal  chords,  or 
in  the  power  of  lengthening  and  shortening  them;  but  it  is  not 
yet  fully  understood.  The  difference  between  a  bass  and 
tenor,  as  between  a  contralto  and  soprano  voice,  is  probably 
that  of  quality  only,  like  that  between  different  kinds  of  musical 
instruments. 

7.  What  is  the  number  of  vibrations  per  second  necessary  to 
produce  the  fifth  tone  of  the  scale  of  C  ? 

(p.  176.)  Ct  =  128  vibrations.    G  of  that  scale  =  192  vibrations  per  second. 

8.  What  is  the  length  of  each  sound-wave  in  that  tone  when 
the  temperature  is  zero  ? 

1090  ft.—  32  ft. =1058  ft,    1058  ft.  -t- 192=5  ft.  6  -I-  in.  (the  length  of  each  vibration). 

9.  What  is  the  number  of  vibrations  in  the  fourth  fane  above 
middle  C  (CJ  ? 

f^n 

C8  =  256  vibrations  .  fii  _  (the  proportionate  no.  for  the  5th  of  tho  scale). 

256  x  —  =  384  (the  number  of  vibrations  per  second). 

2* 


34  ANSWERS  TO  PRACTICAL  QUESTIONS 

10.  A  meteor  of  Nov.  13,  1868,  is  said  to  have  exploded  al 
a  height  oj '60  miles :  what  time  would  have  been  necessary  for 
its  sound  to  reach  the  earth  ? 

5280  ft.  x  60  =  310,800  ft. 
316,800  ft.  -*- 1090  ft.  =  290  (sec.)  =  4  min.  50  gee. 

11.  A  stone  was  let*fall  into  a  well,  and  in  4  seconds  was 
heard  to  strike  the  bottom.     How  deep  was  the  well? 

(See  p.  48.)  d  =  16  x  f».        d  =  16  x  42  =  256  ft. 

1 2.  What  lime  would  it  require  for  a  sound  to  travel  5  miles 
in  tke  still  water  of  a  lake  ? 

6280  ft.  x  5  =  26,400  ft. 
26,400  ft.  -i-  4700  ft.  =  5.0  (sec.) 

13.  How  much  louder  will  be  the  report  of  a  gun  to  an 
observer  at  a  distance  of  20  rods  than  to  one  at  half  a  mile? 

160 rod?  are  8 times  20  rods.  The  intensity  of  the  sound  is  inversely  as  the 
square  of  the  distance  =  1/64.  Hence  the  sound  is  64  times  louder  to  the 
observer  at  20  rods  that  to  the  one  at  half  a  mile. 

14.  Does  sound  travel  faster  at  the  foot  or  at  the  top  of  a 
mountain  ? 

The  density  and  elasticity  of  the  air  vary  in  the  same  pro- 
portion ;  hence  if  the  temperature  were  the  same  on  the  top  of 
a  mountain  that  it  is  at  the  foot,  the  velocity  of  sound  would 
be  the  same,  but  as  it  is  always  colder,  the  velocity  is  less. 

15.  Why  is  an  echo  weaker  than  the  original  sound? 
Because  the  intensity  of  the  sound-wave  is  weakened  at  each 

reflection. 

1 6.  Why  is  it  so  fatiguing  to  talk  through  a  speaking- 
trumpet  ? 

Because  so  much  more  air  must  be  set  in  motion  by  the 
vocal  chords.  The  column  of  air  in  the  resonant  cavity  of 
the  throat  is  re-enforced  by  all  the  air  in  the  trumpet. 

•  -When  we  hear  a  goblet  or  a  wine-glass  struck  with  the 
blade  of  a  knife,  we  can  distinguish  three  sounds,  the  funda- 
mental and  two  harmonics.  * 

*  Is  not  the  ear  the  most  perfect  sense  ?  A  needlewoman  will  distinguish  by 
the  pound,  whether  it  is  silk  or  cotton  that  is  torn.  Blind  people  recognise 


IN  NATURAL  PHILOSOPHY.  35 


OPTICS. 

224.  i .    Why  is  a  secondary  bow  fainter  than  the  primary  / 
The  primary  is  produced  by  one  reflection  and  two  refrac- 
tions; the  secondary,  by  two  reflections  and  two  refractions. 
The  additional  reflection  weakens  the  ray. 

Why  are  the  colors  reversed? 

We  can  understand  this  by  looking  at  Fig.  159.  In  one 
bow  we  see  that  the  rays  enter  the  drops  at  the  top,  and  are 
refracted  at  the  bottom  to  the  eye ;  in  the  other,  that  the  rays 
enter  at  the  bottom,  and  are  refracted  at  the  top  to  the  eye. 

2.  Why  can  we  not  see  around  a  house  or  through  a  bent  tube  f 
The  rays  of  light  move  in  straight  lines. 

3.  What  color  would  a  painter  use  if  he  wished  to  represent 
an  opening  into  a  dark  cellar  f 

Black. 

4..  Is  black  a  color? 
No ;  it  is  the  absence  of  color. 
Is  white  f 

Yes ;  it  is  the  presence  of  all  color — i.  e.,  it  is  the  compound 
effect  produced  on  the  brain  by  seven  different  impressions. 

5.  By  holding  an  object  rearer  a  light,  will  it  increase  or 
diminish  the  size  of  the  shadow  ? 

It  will  increase  it,  because  more  rays  are  intercepted. 
7.    Where  do   w?    see  a  rainbow  in  the  morning? 
In  the  west. 

the  age  of  persons  by  their  voices.  An  architect,  comparing  the  length  o* 
two  lines  separated  from  each  other,  if  he  estimate  within  the  30th  part,  we 
deem  very  accurate ;  but  a  musician  would  not  be  considered  very  precise 
who  only  estimated  within  a  quarter  of  a  note.  (128-*-30  =  4,  nearly.)  In  a 
large  orchestra,  the  leader  will  distinguish  each  note  of  each  instrument.  We 
recognize  an  old-time  friend  by  the  sound  of  his  voice,  when  the  other  senses 
utterly  fail  to  recall  him.  The  musician  carries  in  his  ear  the  idea  of  the 
musical  key  and  every  tune  in  the  scale,  though  he  is  constantly  hearing  a 
multitude  of  sounds.  A  tune  once  learned  will  be  remembered  when  the 
words  of  the  song  are  forgotten.  Prof.  Pepper  tells  us  that  he  tuned  a  fork 
which  corresponded  to  64,000  vibrations  per  second.  The  first  harmonic  ia 
produced  by  one-half  the  whole  cord,  the  second  by  one-third,  «fec. 


36  ANSWERS  TO  PRACTICAL 

8.  Can  any  two  spectators  see  the  same  rainbow  ? 

They  cannot,  because  no  two  persons  can  be  at  the  right 
angle  to  get  the  same  color  from  a  drop. 

9.  Why,  when  the  drops  of  water  are  falling  through  the 
air,  does  the  bow  appear  stationary  ? 

Because  the  drops  succeed  each  other  so  rapidly  that  they 
keep  a  constant  impression  on  the  retina. 

10.  Why  can  a  cat  see  in  the  night? 

Because  the  pupils  of  its  eyes  are  larger,  and  so  admit  more 
light. 

Why  cannot  an  owl  see  in  daylight  ? 

The  pupils  of  its  eyes  are  large  enough  to  admit  of  cleai 
vision  in  the  night,  but  they  cannot  be  contracted,  and  so  in 
daylight  the  owl  becomes  dazzled  with  the  excess  of  light 
received. 

12.  Why  are  we  blinded  when  we  pass  quickly  from  a  dark 
into  a  brilliantly  lighted  room  ? 

The  pupils  of  our  eyes  admit  too  much  light,  but  they  soon 
contract  to  the  proper  dimensions,  and  we  can  then  see  dis- 
tinctly. When  we  pass  out  from  a  lighted  room  into  the  dark 
street,  the  conditions  are  reversed. 

*     13.  If  the  light  on  a  distant  planet  is  only^  that  which  we 
receive,  how  does  its  distance  from  the  sun  compare  with  ours  ? 
As  the  light  is  inversely  as  the  square  of  the  distance,  the 
distance  is  1/100=  10  times  greater  than  ours. 

14.  If  when  I  sit  6  feet  from  a  candle  I  receive  a  certain 
amount  of  light,  how  much  will  I  diminish  it  if  I  sit  back  6 
feet  further  ? 

As  my  distance  from  the  light  is  doubled,  the  light  is  in- 
versely as  22,  or  only  \  as  bright. 

15.  Why  do  drops  of  rain,  in  falling,  appear  like  liquid 
threads  ? 

The  impression  the  drop  makes  on  the  retina  remains  until 
the  drop  reaches  the  ground. 

'*>.    Why  does  a  to~~'d  turn  darker  when  ivetf 


IN  NATURAL  PHILOSOPHY.  37 

More  of  the  light  is  transmitted,  and  less  reflected.  We  see 
this  illustrated  in  greasing  a  bit  of  paper.  It  becomes  semi- 
transparent  because  more  light  passes  through  it,  but  looks 
darker  itself  because  less  light  is  reflected  to  the  eye. 

1 7.  Does  color  exist  in  the  object  or  in  the  mind  of  the  ob- 
server ? 

In  the  mind.  Color  in  the  object  can  be  only  a  peculiar 
property  whereby  a  body  absorbs  some  colors,  and  reflects  or 
transmits  others. 

1 8.  Why  is  lather  opaque,  while  air  and  a  solution  of  soap 
are  each  transparent  ? 

By  repeated  reflections  and  refractions  in  passing  through 
the  unhomogeneous  mass  of  lather,  the  rays  are  weakened. 
The  principle  is  the  same  as  that  of  deadening  floors  with  tan- 
bark.  (Phil.,  p.  161.) 

19.  Why  does  it  whiten  molasses  candy  to  pull  it? 

Water  is  given  up  both  in  cooking  and  pulling.  This  causes 
more  light  to  be  reflected  (Q.  16),  while  the  crystals  formed,  es- 
pecially on  the  surface,  hide  the  impurities. 

20.  Why  does  plastering  become  lighter  in  color  as  it  dries  ? 
Because,  as  the  water  evaporates,  the  mortar  transmits  less 

light,  and  reflects  more  light  to  the  eye.   . 

i 1 .  Why  does  a  photographer  use  a  kerosene  oil-lamp  in  the 
"dark-ro'om?" 

Kerosene  oil-flame  emits  only  heat  and  color,  but  no  actinic 
rays.  Some  ' '  dark-rooms"  are  lighted  with  yellow  glass  windows. 

22.  Is  the  common   division   of  colors   into    "cold"   and 
"warm"  verified  in  philosophy? 

Yes ;  red  contains  more  heat  than  violet. 

23.  Why  is  the  image  on  the  camera,  Fig.  167,  inverted? 
The  rays  cross  each  other  at  the  focus  of  the  double  convex 

lens 

24.  Why  is  the  second  image  seen  in  the  mirror,  Fig.  134, 
brighter  than  the  firct? 

The  first  is  formed  by  reflection  from  the  glass,  and  the 
second  from  the  mercury.  As  the  latter  is  a  better  reflector, 


38  ANSWERS  TO  PRACTICAL  QUESTIONS 

the  second  image  will  be  brighter.    Each  image  after  that  will 
be  weakened  by  the  repeated  reflection. 

27.  Which  can  be  heard  at  the  greater  distance,  noise  or 
music  f 

Other  things  being  equal,  music  will  penetrate  much  further 
than  noise.  Boatmen  call  to  each  other,  at  a  distance,  in  a 
musical  tone.  A  band  is  heard  above  the  noise  of  the  rabble. 
It  seems  to  be  a  wise  arrangement  of  Providence  that  all  harsh, 
discordant  noises  should  perish  as  soon  as  possible,  and  only 
harmonious  ones  survive. 

28.  Why  are  some  bodies  brilliant,  and  others  dull? 

Some  reflect  the  light  better  than  others.  A  piece  of  stone 
coal  lying  in  the  sun's  rays  will  shine  so  brilliantly  that  one 
will  cease  to  see  the  coal  at  all,  and  will  judge  it  to  be  a  bright 
metal. 

29.  Why  can  a  carpenter  looking  along  the  edge  of  a  board 
tell  whether  it  is  straight  ? 

If  the  edge  is  straight,  the  light  will  be  reflected  uniformly 
to  his  eye  from  the  whole  length.  Any  uneven  places  will 
make  dark  and  light  spots. 

30.  Why  can  we  not  see  out  of  the  window  after  we  have 
lighted  the  lamp  in  the  evening  f 

The  glass  reflects  the  light  of  the  lamp  back  to  our  eyes, 
and  they  adapt  themselves  to  the  increased  amount. 

3 1 .  Why  does  a  ground-glass  globe  soften  the  light  ? 
It  scatters  the  rays. 

32.  Why  can  we  not  see  through  ground-glass  or  painted 
windows  ? 

They  transmit  the  light  irregularly  to  the  eye,  and  not 
uniformly,  like  a  transparent  body. 

33.  Why  does  the  moon's  surface  appear  flat  ? 

Because  it  is  so  distant  that  the  eye  cannot  detect  the  dif- 
ference between  the  distance  of  the  centre  and  the  circumfer 
ence. 


IN  NATURAL  PHILOSOPHY.  39 

34.  Why  can  we  see  further  with  a  telescope  than  with  the 
naked  eye  ? 

Because  it  furnishes  us  more  light  with  which  to  see  a  dis- 
tant object. 

35.  Why  is  not  snow  transparent,  like  ice? 
Because  it  is  unhomogeneous.     See  problem  18. 

36.  Are  there  rays  in  the  sunbeam  which  we  cannot  see  f 
We  cannot  see  the  heat  or  the  chemical  rays. 

37.  ( i )  Make  two  marks  on  a  sheet  of  white  paper,  at  a 
distance  of  about  three  inches  from  each  other.      Then  closing 
one  eye  and  looking  steadily  at  one  mark  (thoiigh  we  can  see 
both),    move  the  paper  toward  the  eye.      A   point  will  be 
reached  where  the  eye  can  perceive  only  one  of  the  marks  /  on 
coming  nearer,  both  will  be  seen  again. 

38.  (2)  Prick  with  a  pin,  through  a  card-board,  two  holes 
:loser  together  than  the  diameter  of  the  pupil  of  the  eye.    Hold- 
ing the  card  pretty  near  the  eyes,  look  through  these  holes  at 
the  head  of  a  pin.     There  will  seem  to  be  two  pin-heads. 

39.  (3)  Press  the  finger  on   one  eyeball  and  we  shall  see 
objects  double. 

Since  an  impression  is  made  on  the  retina  of  each  eye,  it 
would  seem  that  we  ought  always  to  see  objects  double.  The 
nerves  from  both  eyes  are  so  joined,  however,  before  they 
reach  the  brain,  that  this  effect  is  avoided.  If,  now,  we  cause 
the  image  on  the  retina  to  be  made  on  parts  of  the  eye  which 
do  not  correspond  to  each  other,  we  shall  obtain  a  double  image. 

40.  Why  is  a  rainbow  in  the  morning  a  sign  of  foul,  and 
in  the  evening  of  fair  weather? 

In  the  morning  it  indicates  a  formation  of  clouds  when  the 
temperature  is  rising,  and  therefore  shows  a  determination  to 
moisture.  In  the  evening  it  indicates  a  clearing  away  when 
the  temperature  is  falling,  and  hence  shows  a  determination 
to  dryness. 

41.  Why  is  a  red,  lowering  sky  in  the  morning  a  sign,  of 
rain,  and  a  brilliant  red  sky  at  night,  of  fair  weather  f 


4O  ANSWERS  TO  PRACTICAL   QUESTIONS 

42.  Why  does  a  distant  light,  in  the  night,  seem  like  a  starf 

43.  Why  does  a  bright  light,  in  the  night,  seem  so  much 
nearer  than  it  is  ? 

44.  Why  does  a  ray  of  light,  passed  through  a  small  hole, 
of  any  shape,  in  a  card,  make  a  round,  bright  spot? 

45.  Why  are  these  spots  crescent-shaped  during  an  eclipse  ? 

46.  What  color  predominates  in  artificial  lights  ? 
Yellow. 

47.  Why  does  yellow  seem  white,  and  blue  green,  when  seen 
by  artificial  light  ? 

Because  the  white  takes  on,  in  the  yellow  rays,  a  yellow 
hue,  and  the  yellow  added  to  the  blue  gives  a  green,  hence 
there  is  no  white  for  comparison.  So,  also,  dark  blue  be- 
comes purple,  and  red  has  a  tawny  hue.  Magnesium  light 
possesses  all  the  colors  of  the  spectrum,  and  hence  all  objects 
.retain  their  natural  appearance  when  illuminated  by  it. 

48.  Why  are  we  not  sensible  of  darkness  when  we  wink  ? 
Because  the  impression  of  the  light  is  retained  upon  the 

retina  during  the  brief  interval  of  darkness. 

HEAT. 

258.  i.  Why  will  one 's  hand,  on  a  frosty  morning,  freeze 
to  a  metallic  door-knob  sooner  than  to  one  of  porcelain  ? 

Because  the  metal  is  a  better  conductor  of  heat  than  the 
porcelain,  and  hence  conducts  the  heat  from  the  hand  faster. 

2.  Why  does  a  piece  of  bread  toasting  ctirl  up  on  the  side 
toward  the  fire  ? 

The  water  being  expelled  from  the  pores  on  that  side  causes 
the  bread  to  shrink. 

3.  Why  do  double  windows  protect  from  the  cold? 

The  non-conducting  air  enclosed  between  the  window-panes 
keeps  in  the  heat  and  keeps  out  the  cold. 

4.  Why  do  furnace-men  wear  flannel  shirts  in  summer  to 
keep  cool,  and  in  winter  to  keep  warm  f 


IN  NATURAL  PHILOSOPHY.  41 

In  summer  the  non-conducting  flannel  keeps  out  the  fur- 
nace-heat, and  in  the  winter  keeps  in  the  body-heat. 

5.  Why  do  we  blow  our  hands  to  make  them  warm,  and 
our  soup  to  make  it  cool? 

Our  breath  is  warmer  than  our  hands,  but  cooler  than  our 
soup. 

6.  Why  does  snow  protect  the  grass  ? 

The  air  enclosed  between  the  flakes  of  snow  is  a  non-con- 
ductor. No  infant  in  its  cradle  is  tucked  in  more  tenderly 
than  the  coverlet  of  snow  about  the  humble  grass  that  nestles 
down  for  its  winter's  nap  on  the  bosom  of  mother  Earth. 

7.  Why  does  water  "  boil  away"  more  rapidly  on  some  days 
than  on  others  f 

Because  the  atmospheric  pressure  varies. 

8.  What  causes  the  crackling  sound  in  a  stove,  when  a  firs- 
ts lighted? 

The  expansion  of  the  iron  by  the  heat. 

9.  Why  is  the  tone  of  a  piano  higher  in  a  cold  room  than  in 
a  warm  one? 

The  steel  wires  lengthen  in  a  warm  room,  and  so  lower  the 
tone. 

10.  Ought  an  inkstand  to  have  a  large  or  a  small  mouth  ? 
A  small  mouth,  to  prevent  evaporation. 

1 1.  Why  is  there  a  space  left  between  the  ends  of  the  rails  on 
a  railroad  track  ? 

To  allow  room  for  the  expansion  and  contraction  of  the  rails 
with  the  changes  in  temperature. 

12.  Why  is  a  person  liable  to  take  cold  when  his  clothes  are 
damp  ? 

The  water  which  evaporates  from  his  clothes,  in  drying, 
absorbs  heat  from  his  body. 

13.  What  is  the  theory  of  corn-popping? 

The  air  in  the  ceiis  01  trie  corn  expands  by  the  heat  and 
bursts  the  outer  coating  of  the  corn. 


42  ANSWERS  TO  PRACTICAL   QUESTIONS 

14.  Could  vacuum-pans  be  employed  in  cooking? 

They  could  not,  because  the  heat  would  not  be  sufficient  to 
cook  the  food. 

15.  Why  does  the  air  feel  so  chilly,  in  the  spring,  when 
snow  and  ice  are  melting  ? 

When  the  ice  is  passing  into  the  liquid  state,  it  absorbs  heat 
from  all  surrounding  objects. 

1 6.  Why,  in  freezing  ice-cream,  do  we  put  the  ice  in  a 
wooden  vessel,  and  the  cream  in  a  tin  one  ? 

The  non-conducting  wooden  vessel  prevents  the  ice  from 
absorbing  heat  from  the  external  air,  and  the  conducting  tin 
vessel  enables  it  to  absorb  the  heat  from  the  cream. 

1 7.  Why  does  the  temperature  generally  moderate  when  the 
snow  falls  ? 

The  vapor  passing  into  the  solid  form  gives  off  heat. 

19.  Why  does  sprinkling  a  floor  with  water  cool  the  air? 
The  water  turning  to  vapor  absorbs  heat. 

20.  How  low  a  degree  of  temperature  can  be  reached  with 
a  mercurial  thermometer  ? 

Nearly  to  the  freezing  point  of  mercury,  —39°  F. 

21.  If  the  temperature  be  70°  F.,  what  is  it  C.  f 

70*-  32'=38°.    S8-*-1.8=21.r  C. 
— If  the  temperature  be  70°  C.,  what  is  it  F.  ? 
70*  x  1.8=126*.    126" +32°=158*  P. 

22.  Will  dew  form  on  an  iron  bridge  f 
Yes,  because  iron  is  a  good  radiator. 
On  a  wooden  brid&tt  f 

Not  so  readily,  because  wood  is  a  poorer  radiator. 

23.  Why  will  not  corn  pop  when  very  dry  ? 

The  pores  shrink,  and  the  corn  becomes  compact;  only 
porous,  tender-celled  corn  will  pop. 

24.  The  interior  of  the  earth  being  a  melted  mass,  why  do 
we  get  the  coldest  water  from  a  deep  well? 


IN  NATURAL  PHILOSOPHY.  43 

The  well  extends  below  the  influence  of  the  sun,  and  not 
deep  enough  to  reach  the  internal  heat  of  the  earth. 

25.  Ought  the  bottom  of  a  tea-kettle  to  be  polished? 

No,  since  a  polished  surface  would  reflect  the  heat.  We 
need  a  black,  rough,  sooty  surface  to  absorb  the  heat  rapidly. 

26.  Which  boils  the  sooner,  milk  or  water? 

Milk,  because  it  is  so  adhesive  that  the  bubbles  of  steam 
which  are  formed  at  the  bottom  of  the  dish  cannot  easily 
escape.  They  therefore  pile  up  on  top  of  each  other,  and  the 
milk  boils  over  readily. 

27.  Is  it  economy  to  keep  our  stoves  highly  polished? 

The  stove-blacking  used  is  a  good  radiator,  but  the  surface 
should  not  be  highly  polished,  as  that  hinders  radiation. 

28.  If  a  thermometer  be  held  in  a  running  stream,  will  it 
indicate  the  same  temperature  that  it  would  in  a  pailful  of 
the  same  water  ? 

It  will.  For  the  same  reason  that  a  thermometer,  in  the 
wind,  will  indicate  the  same  temperature  as  in  the  still  air. 
although  the  former  seems  to  us  much  colder. 

29.  Which  makes  the  better  holder,  woollen  or  cotton  f 
Woollen,  because  it  is  so  poor  a  conductor  of  heat. 

30.  Which  will  give  out  the  more  heat,  a  plain  stove  or  one 
with  ornamental  designs  ? 

The  latter,  since  it  has  more  radiating  surface 

3 1 .  Does  dew  fall  ? 

No ;  it  forms  directly  where  it  is  found.  The  vapor  merely 
collects  on  the  cold  surface. 

32.  What  causes  the  "  sweating"  of  a  pitcher? 

The  vapor  of  the  air  condenses  on  the  cold  pitcher.  It  is 
often  a  sign  of  rain,  since  it  shows  that  the  air  is  full  of  vapor 
easily  deposited. 

33.  Why  is  evaporation  hastened  in  a  vacuum  f 
Because  the  pressure  of  the  air  is  removed. 


44  AX8WEJSS  TO  PRACTICAL   QUESTIONS 

34.  Does  stirring  the  ground  arotind  plants  aid  in  the  depo- 
sition of  dew? 

It  does,  since  it  facilitates  radiation. 

35.  Why  does  the  snow  at  the  foot  of  a  tree  melt  sooner  than 
that  in  the  open  field? 

The  dark-colored  tree  absorbs  the  sun's  heat,  and  then 
radiates  it  out  in  slow,  dull  waves,  which  are  absorbed  by  the 
snow. 

36.  Why  is  the  opening  in  a  chimney  made  to  decrease  in 
size  from  bottom  to  top  ? 

Because  as  the  heated  air  rises  it  cools  and  shrinks.  If  the 
chimney  did  not  diminish  in  size  correspondingly,  currents  of 
cold  air  would  set  down  from  the  top. 

37.  Will  tea  keep  hot  longer  in  a  bright  or  in  a  dull  tea-pot  * 
In  a  bright  one,  since  a  polished  surface  retards  radiation. 

39.    Why  is  one's  breath  visible  on  a  cold  day  ? 

The  vapor  in  the  breath  is  condensed  by  the  cold  air. 

41.  Why  is  light-colored  clothing  cooler  in  summer  and 
warmer  in  winter  than  dark-colored? 

It  does  not  absorb  the  heat  of  the.  sun  in  summer,  nor  the 
heat  of  the  body  in  winter;  dark- colored  clothing  has  neither 
of  these  desirable  properties. 

42.  How  does  the  heat  at  two  feet  from  the  fire  compare 
with  that  at  four  feet  ? 

22 :  42 : :  1 :  4. 
Hence  it  is  four  times  greater. 

43.  Why  does  the  frost  remain  later  in  the  morning  upon 
some  objects  than  upon  others  ? 

Those  objects  which  are  good  absorbers  of  heat  soon  become 
warm  enough  to  melt  the  frost  upon  them :  "poor  absorbers 
heat  more  slowly,  and  so  retain  the  frost  longer. 

44.  Is  it  economy  to  use  green  wood  ? 

It  is  not,  since  the  sap  must  be  changed  to  vapor,  and  watei 


IN  NATURAL  PHILOSOPHY.  45 

m  turning  to  vapor  renders  latent  over  900°  of  heat.     This  is, 
of  course,  entirely  lost  to  the  consumer. 

45.  Why  does  not  green  wood  snap  ? 

The  pores  are  filled  with  water  instead  of  air.  The  water 
does  not  expand  rapidly  enough  to  burst  off  the  coverings  of 
the  cells,  and  so  simply  oozes  out  gradually  and  is  vaporized. 

46.  Why  will  a  piece  of  metal  dropped  into  a  glass  or  porce- 
lain dish  of  boiling  water  facilitate  the  ebullition  ? 

The  rougher  surface  of  the  metal  aids  in  the  formation  and 
disentanglement  of  the  steam-bubbles.  The  bubbles  cling 
longer  to  a  smooth  than  to  a  rough  surface.  This  is  one 
cause  of  that  bumping  sound  often  noticed  when  liquids  are 
boiling  in  glass  dishes. 

47.  Which  can  be  ignited  the  more  easily  with  a  burning- 
glass,  black  or  white  paper  f 

Black  paper,  since  it  is  a  much  better  absorber  of  heat. 

48.  Why  does  the  air  feel  colder  on  a  windy  day  ? 
Because  fresh  portions  of  cold  air  are  brought  constantly  in 

contact  with  our  bodies. 

49.  In  what  did  the  miracle  of  Gideon 's  fleece  consist  ? 
The  hard  threshing-floor  was  a  better  conductor  of  heat 

than  the  porous  fleece ;  hence,  naturally,  the  dew  would 
collect  on  the  latter  more  readily  than  en  the  former.  In 
the  miracle,  the  conditions  remaining  the  same,  the  results 
in  the  two  cases  were  reversed.  (Judges,  vi.  37-40.) 

50.  Could  a  burning-lens  be  made  of  ice  ? 

Burning-lenses  have  been  made  of  that  material.  The  rays 
have  no  heating  power  until  the  waves  of  ether  are  stopped. 
They  do  not  elevate  the  temperature  of  the  medium  through 
which  they  pass. 

5 1 .  Why  is  an  iceberg  frequently  enveloped  by  a  fog  ? 
The  moisture  of  the  air  is  condensed  upon  its  cold  surface. 

52.  Would  dew  gather  more  freely  on  a  rusty  stove  than  on 
a  bright  kettle? 

It  would,  because  the  rusty  iron  surface  is  a  good  radiator. 

53.  Why  is  a  clear  night  colder  than  a  cloudy  one  f 


46  ANSWERS  TO  PRACTICAL  QUESTIONS 

On  a  cloudy  night  the  clouds  reflect  the  radiated  heat  of  the 
earth  back  again,  and  thus  act  as  a  blanket  to  keep  the  earth 
warm.  On  such  a  night  there  can  be  no  frost  or  dew.  On  a 
clear  night,  the  heat  which  the  earth  radiates  passes  out  freely 
into  space,  and  thus  the  earth  cools  rapidly. 

•  54.    Why  is  no  dew  formed  on  cloudy  nights  f 
See  last  question. 

55.  Water  boiled  at  a  certain  place  at  200°  F.  :  what  wa* 
the  height  above  the  sea  f 

56.  On  Mont  Blanc  boiling  water  is  only  84°  C.  :  what  is 
the  height? 

57.  Why  do  we  use  a  longer  tube  of  mercury  for  a  barometer 
than  a  thermometer  ? 

58.  Which  is  the  hottest  part  of  a  room  ? 

59.  Why  is  it  hotter  above  a  flame  than  at  the  side  f 

60.  What  is  the  difference  between  dew  and  rain  f 

6 1 .  Why  will  ashes  keep  fire  overnight  ? 

62.  If  a  pane  of  glass  and  a  similar  plate  of  polished  steel 
were  laid  upon  the  ground,  in  the  night,  upon  which  would 
the  dew  form  most  abundantly  ? 

The  glass  is  a  poor  conductor  of  heat,  and  so  would  absorb 
little  heat  from  the  earth,  while  the  metal  would  absorb  it 
freely ;  the  glass  is  a  better  radiator  than  the  polished  metal, 
and  thus  would  become  drenched  with  dew,  while  the  metallic 
surface  would  be  scarcely  dimmed. 

63.  Why  is  there  but  little  dew  formed  in  cities  ? 

64.  Is  an  abundant  dew  a  sign  of  rain  f 
It  is.     See  question  32. 

65.  Is  there  any  dew  formed  out  at  sea  ? 

66.  Why  are  gardens  in  a  valley  often  touched  with  frost, 
while  those  on  the  hills  escape  unharrf.ed  / 

The  cold  air  settles  into  the  valley;  while  the  warm  air  rises 
to  the  hills. 


IN  NATURAL  PHILOSOPHY.  47 

67.  How  are  hailstones  formed? 

There  are  two  separate  currents  of  air,  one  hot  and  charged 
with  moisture,  the  other  cold.  The  former  is  displaced  by 
the  latter  and  driven  up  in  the  atmosphere.  There  its  vapor 
is  condensed  at  the  centre  of  the  cloud  into  snow,  and  at  the 
extremities  into  ice-cold  water.  In  this  cloud  there  is  a  whirl- 
ing motion  which  collects  the  snow  into  little  balls,  each  of 
which  is  the  nucleus  of  a  hailstone.  Each  of  these  is  carried, 
alternately,  by  the  whirling  currents,  into  the  snow-cloud  at 
the  centre,  and  the  ice-cold  water  outside.  Both  give  it  a 
coating,  one  of  snow-like,  spongy  ice,  and  the  other  of  trans- 
parent ice.  This  is  done  with  great  rapidity,  until  at  last  its 
weight  overcomes  the  violent  upward  motion  which  sustains  it 
in  the  air,  and  the  hailstone  falls  to  the  ground.  When  a 
hailstone  is  carefully  examined  we  can  see  this  nucleus,  and 
these  concentric  layers,  like  the  coats  of  an  onion.  * 

68.  Why  do  we  have  hailstorms  in  summer,  and  not  in 
•winter? 

The  small  spongy  hail  or  sleet  of  winter  has  the  same  origin 
as  hailstones  in  summer,  but  there  is  not  enough  vapor  in  the 
cold  air  to  give  them  the  size  of  summer  hailstones. 

69.  Is  the  sweating  of  a  pitcher  a  sign  of  rain  ? 
See  question  32. 

70.  Where  should  ice  be  applied,  to  cool  water? 
At  the  top,  because  cold  water  falls. 

71.  Why  is  evaporation  hastened  in  a  vacuum? 
Because  the  pressure  of  the  air  is  removed. 

72.  Is  a  dusty  boot  hotter  to  the  foot  than  a  polished  one  ? 
It  is,  because  it  is  a  better  absorber  of  heat. 


*  The  above  theory  is  that  advanced  by  Prof.  Loomis,  in  his  "Treatise  on 
Meteorology."    Th  >  teacher  will  find  thii  work  invaluable  on  all  raeteorologi- 

cal  questions. 


48  ANSWERS  TO  PRACTICAL 

(Key,  p.  34,  Prob.  n.)  The  method  adopted  in  solving 
this  problem  is  merely  the  rough  one  in  common  use,  and 
gives  only  an  approximate  result.  If  an  exact  answer  is  de- 
sired, we  should  take  in  account  the  time  required  for  the  sound 
to  reach  the  ear.  The  following  method  may  be  employed : 

aj  =  No.  sec.  for  stone  to  fall. 
4— a  =      "         "  sound  to  reach  the  ear. 
16x2  =  (4  — a:)1090. 
16a;a  =  4360  — 1090a;. 

From  this,  by  completing  the  square,  we  have 

a  =  3.7892+  seconds. 
Then  the  equation  (2)  d  =  i6/2  gives  the  depth. 

d  =  16(3.7892 +)2  =  229  ft.  and  8.795  in., 
which  is  the  answer  exact  within  a  small  fraction. 
A  second  method  (more  exact) — 

d  =  depth  of  the  well  =  16ia. 


4—  i  y/d  =  No.  of  sec.  for  sound  to  reach  the  eftZ. 
(4-i  v/d)l090  =4360  - 


_  __  190Q8SOC. 


A  N  S  W  E  B  S 

TO  THE  PRACTICAL  QUESTIONS, 

AND  SOLUTIONS  OF  THE  PROBLEMS, 

m  THE 

FOURTEEN  WEEKS   COUKSE 

IN 

CHEMISTRY, 


f  The  bold-faced  figures  refer  to  the  page  of  the  Chemistry;  the  others  to 
th*  number  of  the  Practical  Questions."] 


1.  Is  it  likely  that  all  the  elements  have  been  discovered? 

It  is  not,  since  several  have  been  found  lately  by  means  of 
spectrum  analysis.  The  ancients  held  that  there  are  but  four 
elements — earth,  water,  air,  and  fire ;  the  first  representing 
the  solid  form  of  matter,  the  second  the  liquid,  the  third  the 
gaseous,  and  the  fourth  the  force  which  changes  matter  from 
one  form  to  another.  Few  of  the  sixty-five  elements  are  com- 
mon. Those  italicised,  in  the  table  on  page  14,  are  rare. 
The  remarkable  phenomena  of  allotropism  would  seem  to  in- 
dicate that,  perhaps,  what  we  now  consider  distinct  elements 
nay  be  only  allotropic  states  of  the  same  element.  Indeed, 
it  is  possible  to  conceive  that  all  substances. are  only  allotropic 
forms  of  one  universal  essence.  In  the  present  state  of 
chemistry  this  view  cannot  be  proved,  and  is  only  a  specula- 
t'on  as  to  what  may  be  discovered  in  the  future. 

2.  What  is  the  origin  of  the  term  "gas?" 

This  word  was  first  used  in  the  iyth  century.  Explosion^, 
strange  noises,  and  lurid  flames  had  been  seen  in  mines,  caves, 
&c,  The  alchemists,  whose  earthen  vessels  often  exploded 

2 


5<D  ANSWERS  TO  PRACTICAL   QUESTIONS 

with  terrific  violence,  commenced  their  experiments  with 
prayer,  and  placed  on  their  crucibles  the  sign  of  the  cross — 
hence  the  name  crucible  from  crux  (gen.  crucis),  a  cross.  All 
these  manifestations  were  supposed  to  be  the  work  of  invisible 
spirits,  to  whom  the  name  gahst  or  geist,  a  ghost  or  spirit, 
was  applied.  The  miners  were  in  special  danger  from  these 
unseen  adversaries,  and  it  is  said  that  their  church  service  con- 
tained the  petition,  ''From  geists,  good  Lord,  deliver  us!" 
The  names — spirits  of  wine,  nitre,  &c.,  are  a  relic  of  the 
superstitions  of  that  time. 

3.  If  the  air  iv ere  pure  O,  what  bodies  would  escape  com- 
bustion in  a  conjlagration  ? 

The  stones,  mortar,  &c.,  which  being  already  combined 
with  O  and  other  elements,  and  having  their  chemical  affinities 
satisfied,  are  hence  termed  "burnt  bodies." 

4.  Why  will  lime  added  to  hard  water  often  soften  it  ? 
The  lime  will  combine  with  the  free  carbonic  acid  absorbed 

by  the  water.  This  renders  the  water  incapable  of  holding  in 
solution  as  much  carbonate  of  lime  as  before,  which  is  then 
precipitated,  and  the  water  thus  partly  softened. 

5.  Why  will  stirring  a  wood  fire  quicken  the  flame,  but  a 
coal  fire,  will  deaden  it  ? 

Stirring  a  fire  lets  in  more  O,  which  quickens  a  wood  fire 
but  reduces  the  temperature  of  a  coal  fire  below  the  point  of 
union  between  O  and  coal.  It  is  really  based  on  the  fact  that 
a  higher  temperature  is  requisite  to  burn  coal  than  wood. 

6.  Why  does  blowing  on  a  fire  quicken  the  flame,  but  on  a 
lamp  extinguishes  it  ? 

The  same  principle  applies  as  in  the  last  question.  In  ad- 
dition, the  force  of  our  breath  often  drives  the  flame  off  the 
wick  mechanically. 

7.  Why  will  oyster-shells  placed  on  the  grate  of  a  coal  Jire 
prevent  the  formation  of  clinkers? 

The  lime  of  the  shells  forms  a  flux  with  the  silicates  con- 
tained in  the  coal,  and  thus  renders  them  more  fusible. 


IN  CHEMISTRY.  51 

8.    What  alkali  abounds  in  sea-weed? 
Soda. 

g.    What  alkali  abounds  in  land-plants  ? 

Potash.  The  former  salt  is  a  constituent  of  sea-water,  and  the 
latter  of  rocks  which  decompose  to  form  the  soil. 

10.  How  is  lime-water  made  from  oyster-shells  ? 

The  oyster-shells,  in  burning,  lose  their  CO2.  This  leaves  the 
lime  uncombined  ;  hence  it  readily  dissolves  in  water. 

1 1.  What  other  tests  of  lead  than  HS  ? 

KI  gives  a  yellow  precipitate,  NH4S  a  black,  and  SO3  a  white 
one. 

12.  Will  not  lime   lose   its   beneficial  effect   upon   soil  after  a 
time  ? 

Lime  acts  in  various  ways  to  improve  the  fertility  of  a  soil. 
It  corrects  its  acidity,  aids  in  the  decomposition  of  the  rocky  con- 
stituents, hastens  the  decay  of  the  humus,  and  also  makes  the 
soil  more  porous.  It  does  not,  however,  benefit  the  growing 
plant  directly,  but  works  up  other  materials  in  the  soil.  It 
therefore  loses  its  effect  after  a  time.  The  Belgian  farmers  have 

a  proverb : 

"  Much  lime  and  no  manure 
Make  farm  and  farmer  poorer." 

13.  What  is  the  derivation  of  the  term  zinc  ? 

The  name  is  probably  derived  from  the  Germnn  zinken,  signi- 
fying "  nails,"  and  is  applied  to  this  metal  on  account  of  its  fre- 
quently forming  pointed  particles  somewhat  resembling  nails, 
when  melted  and  suddenly  poured  into  water.  (Griffiths.) 

14.  What  is  the  action  of  permanganate  of  potash  (chameleon 
mineral)  as  a  disinfectant? 

It  gives  up  its  O  to  oxydize  the  organic  impurities  of  the  water 
in  which  they  collect. 

15.  Do  all  fish  die  when  taken  out  of  the  water? 

No.  Some  fish  have  an  apparatus  for  moistening  their  gills. 
They  can  therefore  crawl  about  in  the  grass,  and  even  migrate 
from  one  stream  to  another. 


52  ANSWMliS  TO  PRACTICAL   QUESTIONS 

1 6.  What  proof  have  we  that  H  is  a  metal? 

Besides  that  given  in  the  Chemistry,  the  "  sodium  amalgam" 
is  thought  by  some  to  be  an  additional  proof.  Heat  moderate- 
ly in  a  test-tube  a  little  mercury  with  a  grain  or  two  of  sodium. 
The  two  metals  will  combine,  forming  a  pasty  amalgam. 
When  cold,  pour  over  it  a  solution  of  sal-ammoniac.  The 
amalgam  will  immediately  swell  up  to  eight  or  ten  times  its 
original  bulk,  retaining,  however,  its  metallic  lustre.  It  is 
thought  that  H  is  the  metal  which  puffs  out  and  combines 
with  the  mercury,  since  otherwise  we  would  be  compelled  to 
suppose  that  NH4  is  a  metallic  element,  instead  of  a  com- 
pound radical,  as  is  generally  believed. 

17.  Why  does  not  frozen  meat  spoil? 

The  cold  protects  from  chemical  change.  The  bodies  of 
mammoths  have  been  found  in  the  frozen  soil  of  Arctic  regions 
so  perfectly  preserved  that  the  dogs  ate  the  flesh.  How  long 
the  animals  had  been  there  we  cannot  tell,  but  certainly  for 
ages.  In  1861  the  mangled  remains  of  three  guides  were 
found  at  the  foot  of  the  Glacier  de  Boissons,  in  Switzerland. 
They  had  been  lost  in  an  avalanche  on  the  grand  plateau  of 
Mont  Blanc,  forty-one  years  before. 

1 8.  Give  an  illustration  of  the  effect  of  food  on  the  disposi- 
tion of  animals. 

Bears  which  feed  on  acorns  are  mild  and  tractable,  while 
those  of  the  polar  regions,  which  live  on  flesh  alone,  are  fierce 
and  ungovernable. 

19.  Compare  the  chemical  action  of  the  animal  with  that  of 
the  plant. 

The  animal  lives  on  organized  materials,  taking  up  O  and 
evolving  CO2,  and  other  oxydized  products.  The  plant  lives 
on  unorganized  materials,  CO2,  HO,  NH,,  and  salts,  organ- 
izing them  and  evolving  O.  The  function  of  the  animal  is 
oxydation;  that  of  the  plant,  reduction.  The  food  of  the 
plant  serves  merely  to  increase  its  bulk ;  that  of  the  animal  is 
employed  to  replace  the  material  worn  out  by  the  active  opera- 
tions of  life.  The  animal  obtains  the  energy  necessary  for  its 


L\   CHEMISTRY.  53 

existence  from  the  oxydation  of  its  own  body;  the  plant  ob- 
tains the  energy  necessary  for  the  organization  of  its  food  di 
rectly  from  the  sun. 

20.  Show  how  man  is  made  mainly  of  condensed  air. 

Science  has  demonstrated  that  man  is  formed  of  condensed 
air  ;  that  he  lives  on  condensed  as  well  as  uncondensed  air, 
and  clothes  himself  in  condensed  air,  that  he  prepares  his 
food  by  means  of  condensed  air,  and  by  means  of  the  same 
-agent  moves  the  heaviest  weights  with  the  velocity  of  the 
wind.  But  the  strangest  part  of  the  matter  is,  that  thou- 
sands of  these  tabernacles  formed  of  condensed  air,  and  going 
on  two  legs,  occasionally,  and  on  account  of  the  production 
and  supply  of  these  forms  of  condensed  air  which  they  re- 
quire for  food  and  clothing,  or  on  account  of  their  honor  and 
power,  destroy  each  other  in  pitched  battles  by  means  of  con- 
densed air.  —  LlEBlG. 

19.  i.  In  making  O  from  chlorate  of  potash  (KO.CIOJ, 
how  much  can  be  obtained  from  two  pounds  of  the  salt? 

6O=48=equivalent  of  constituent. 
KO.C1O6=122.5=          "        "  compound. 

a:=weight  of  constituent. 
21bs.=      "       "  compound. 
60  :  KO.ClOfi  :  :  x  :  2  Ibs. 
48  :  122.5  :  :  x  :  2  Iba. 


2.  In  making  H,  sine  is  used.    How  much  sulphate  of  zitic 
will  be  formed  from  2.  Ibs.  of  the  metal* 


Zn  =  32.5  =  equivalent  of  the  constituent. 
ZnO.SO3-f7HO  =  143.6=  "  "      compound. 

2  Ibs.  =  weight  of  the  constituent. 
x=      "  "      compound. 

Zn  :  (ZnO.SO3+7HO)  ::  2  Ibs.  :  x. 

32.5  :  143.6  :  :  2  Ib.  :  x. 
a;=8.8  Ibs.  (white  vitriol,  sulp.  zinc). 

3.  How  much  SO3  will  be  required  to  make  50  Ibs.  sulphate 
of  iron  (FeO.SO^-jHO)  ? 


54  ANSWERS  TO  PRACTICAL    QUESTIONS 

SO3  =  40  =  equivalent  of  the  constituent. 
FcO.SO,+7HO  =  139  =          t4  "      compound. 

x  =  weight  of  the  constituent. 
50  Ibs.  =       "         *'       compound. 
SOS  :  (FeO.SO3-i-7HO)  ::  x  :  50  Ibs. 
40  :  139  : :  x  :  50  Ibs. 
x  =  14  /'/gibs.  (SO 3.) 

4.  The  equivalent  of  the  chloride  of  sodium  -(salt)  is  58. 5. 
In  10  Ibs.  there  are  6t  rr  Ibs.  of  chlorine  :  what  is  the  equiva* 
lent  of  Cl? 

x  =  equivalent  of  the  given  constituent. 
58.5=         "  "          "      compound. 

6  if  7  Ibs.  =  weight  of  the  given  constituent- 
10  Ibs.  =       "        "          "     compound. 
x  :  58.5  : :  6  -,  f  T  Ibs.  :  10  Ibs. 
x  =  35.5. 

5.  In  20  grains  of  bromide  of  potassium   there  are  6^9 
grains  of  potassium :  the  equivalent  of  potassium  being  39, 
what  is  the  equivalent  of  the  bromide  of  potassium  ? 

89  =  equivalent  of  the  given  constituent. 
x=         "  "          "     compound. 

6  ~ffe  gre«  =  weight  of  the  given  constituent. 
SOgre.  =       »*         "         "     compound. 
39  :  x  : :  6  -^  grs.  :  20  grs. 
a?  =119. 

6.  In  14  Ibs.  of  iron-rust  (Fe^O^  how  much  O? 

3O  =  24  =  equivalent  of  the  given  constituent. 
PeaO8  =  80  =         "  "          "     compound. 

*  =  weight  of  the  given  constituent. 
14  Ibs.  =       "        "          "      compound. 
24  :  80  : :  x  :  14  Ibs. 
a;  =  4  Vilbs.  (O). 

7.  In  20  Ibs.  of  glass  (NaO.SiO^  +  CaO.SiOJ  how  many 
tt>s.  of  sand  (SiOJ  ? 

2  SiO2  =   <!0  =  equivalent  of  the  given  constituent. 
(NaO.SiO2  +  CaO.SiO2)  =  119=         "  "  "      coapound. 

x  =  weight  of  the  given  constituent. 
80  Ibs.  =        *'         '•         "      compound. 
60:  119: :  x:  20 Ibs. 
X  =  10  ^  Ibs.  (SiOj) 


IN  CHEMISTRY.  55 

8.  In  a  25  Ib.  sack  of  salt  (NaCl)  how  many  Ibs.  of  the 
metal  sodium  ? 

Na  =  23  =  equivalent  of  the  constituent. 
NaCl  =  58.5=.         "  "       compound. 

x  =  weight  of  the  constituent. 
25  Ibs.  =      "         "      compound. 
23  :  58.5  : :  x  :  25  Ibs. 
a;  =  9-^- Ibs.  (Na). 

229.  5.  What  weight  of  O  is  contained  in  60  grs.  of 
KO.CIOJ 

,O  =  48  =  equivalent  of  constituent. 
KO.C106  =  122Va  =        "  "  compound. 

x  =  weight  of  constituent. 
60  grs.  =      "       "  compound. 
48  :  122V3  : :  x  :  60  grs. 
X  =  23  |f  grs.(O). 

6.  How  much  KCl  will  be  formed  in  preparing  80  grs.  of  Of 
First  find  how  much  KO.C1O6  will  be  required  to  make  80 

grs.  «f  O,  and  then  subtract  the  80  grs.  of  O  from  the  amount, 
and  the  remainder  will  be  the  KCl.  The  constituent  and 
compound  are  the  same  as  in  the  last  problem. 

48  :  122  »/a  : :  80  grs.  :  x 

x  =  204.16  grs. 
204.16  grs.  —  80  grs.  =  124.16  grs.  (KCl). 

7.  How  much  H  can  be  made  from  10  Ibs.  of  Zn  f 

First  find  how  much  ZnO  10  Ibs.  of  Zn  will  form  ;  second, 
subtract  the  10  Ibs.  of  Zn,  and  the  remainder  is  the  O  which 
came  from  the  water.  This  O  formed  f  of  the  water,  and 
the  remaining  £  is  the  H  set  free. 

Zn  =  32.5  =  equivalent  of  the  constituent. 
ZnO  =  40.5  =        "  "       compound. 

10  Ibs.  =  weight  of  the  constituent. 
x=        "         "      compound. 

35.5  :  40.5  : :  10  Ibs.  :  x. 

OS  ~  12.461  Ibs.  (ZnO).    12.461  Ibs.  ZnO  — 10  Ibs.  Zn  =  2.461  'bs.  (O). 
2.461  Ibs.  H-  8  =  .307  Ibs.  (H). 

8.  How  much  H  can  be  made  from  50  Ibs.  of  water? 


56  AJfSWJSRS  TO  PRACTICAL  QUESTIONS 

H  =  1  =  equivalent  of  given  constituent. 
HO  =  9  =    .       "  "      compound. 

x  =  weight  of  given  constituent. 
50  Ibs.  =        "  "      compound. 

1  :  9  : :  x  :  50  Ibs. 
aj  =  5»/9  Ibs.  (H). 

More  simply,  i  of  water  is  H  ;  hence 
50  Ibs.  +  9  =  5  »/9  Ibs.  (H). 

9.  How  much  saltpetre  will  be  required  to  make  18  lot, 
of  aquafortis  ? 

NO5  =  54  =  equivalent  of  given  constituent. 
KO.NOB  =  101  =          "  "     compound. 

18  Ibs.  =  weight  of  given  constituent. 
x  =        "  "      compound. 

54  :  101  : :  18  Ibs. : x. 
x  =  33  V8  Ibs.  (saltpetre). 

10.  How  much  oil  of  vitriol  will  be  required  to  decompose  6 
Ibs.  of  saltpetre  ? 

First  find  how  much  KO  in  6  Ibs.  of  KO.NO6,  next  how 
much  KO.SO,  that  amount  of  KO  will  make,  and  lastly  sub- 
tract the  KO  from  the  KO.  SO3,  and  the  remainder  will  be  the 
SO,.  In  both  cases  we  neglect  the  HO  combined  in  the  salts 
and  the  acid. 

KO  :  KO.NO5  : :  x  :  6  Ibs. 

47  :  101  : :  x  :  6  Ibs. 

'x  =  2.79  Ibs.  (KO). 

KO  :  KO.S03  : :  2.79  Ibs  :  x. 

47  :  87  : :  2.79  Ibs.  :  x. 

x  =  5.16  Ibs.  (KO.SO8). 

6.16  IDS.  (KO.  S08)  —  2.79  Ibs.  (KO)  =  2.37  Ibs.  (SO8). 

II.  How  much  HO  will  be  decomposed  by  one  drachm  of 
K,  and  how  much  KO  will  be  formed? 

First  find  how  much  KO  I  dr.  of  K  will  form,  then  sub- 
tract from  the  KO  the  drachm  of  K,  and  the  remainder  is  the 
0,  which  must  be  5  of  the  water  from  which  it  is  obtained. 


IN  CHEMISTRY.  57 

K  :  KO  : :  1  dr.  :  x. 

39  :  47  : :  1  dr.  :  x. 
x  =  Igg  drs.  (KO). 

1^%  drs.  —  1  dr.  =  fy  dr.,  the  amount  of  O. 
The  HO  is  9/e  of  8/3»  dr.  =  Vis  dr.  (HO).  9 

12.  What  weight  of  nitrous  oxyd  will  be  formed  from  the 
decomposition  of  6  oz.  of  nitrate  of  ammonia  ? 

2  NO  :  NH4O.N06  : :  x  :  6  oz. 
aj  =  38/j0oz.  (NO). 

13.  How  much  sal-ammoniac  would  be  required  to  make  2 
Ibs.  of  NH^  ? 

NH,  :  NH4C1  : :  2  Ibs.  :  x. 

17  :  53.5  : :  2  Ibs.  :  x. 
jc  =  6Vi7  Ibs.  (sal-ammoniac). 

14.  How  much  CO*  will  be  formed  in  the  combustion  of  30 
grs.  of  CO  f 

CO  :  C0a  : :  30  grs.  :  x. 
14  :  22  : :  30  grs.  :  x. 
a  =  47V7grs.(COa). 

15.  What  weight  of  carbonate  of  soda  (sal-soda)  would  be 
required  to  evolve  12  Ibs.  of  CO^f 

CO,  :  NaO.COa  : :  12  Ibs.  :  x. 

22  :  53  : :  12  Ibs. :  x. 
X  =  28  'Vii  Ibs.  (NaO.CO,). 

1 6.  What  weight  of  bicarbonate  of  soda   (Na 
"soda")  would  evolve  12  Ibs.  of  CO9  ? 

2COa  :  Na0.2CO3  : :  12  Ibs.  :  x. 

44  :  75  : :  12  Ibs.  :  x. 
x  =  20  Vu  Ibs.  ("  soda"). 

17.  What  weight  of  C  is  there  in  a  ton  of  CO9  f 

G  :  CO3  : :  x  :  2000  Ibs. 
6  :  22  : :  x  :  2000  Ibs. 
»=545Vii  Ibs.  (C). 

1 8.  How  much  O  is  consumed  in  burning  a  ton  of  C? 

3* 


58  ANSWERS  TO  PRACTICAL  QUESTIONS 

C  :  C0a  :  :  2000  lbs.  :  x. 

6:2-2::  2000  Ibs.  :  x 

X  =  7333  V3  lbs.  (COa). 

7333  1  /s  —  2000  lbs.  =  5333  Vs  lbs-  (O)« 

More  simply:  — 

C  :  2O  :  :  2000  lbs.  :  a:. 


19.  In  burning  a  charge  of  10  /&?.  #/"  gunpowder,  find  thi 
weight  of  the  several  products  formed. 

(See  page  107.)       (1.)  KS:  (KO.NO3  +  S+3C)  ::  x  :  10  Ibs. 
55  :  135  :  :  x  :  10  lbs. 
a;  =  4  VST  H».  (KS). 

(2.)  N  :  (KO.NO6  +  S+3C)  ::  x  :  10  llw. 
14  :  135  :  :  x  :  10  lbs. 

x  =  1  VST  Ibs.  (N). 

(3.)  3C03  :  (KO.N06  +  S+3C)  :  :  x  :  10  lbs. 
66  :  135  :  :  x  :  10  lbs. 


*  20.    Ff%zl  weight  of  common  salt  would  be  required  to  fonn 
25  /fo.  of  muriatic  acid  (HCl  )  ? 

Cl  :  HCl  :  :  a;  :  25  lbs. 
35.5  :  36.5  :  :  x  :  25  Ibs. 

a;  =  24.3  Ibs.  (Cl). 
Cl  :  NaCl  :  :  24.3  lbs.  :  x. 
85.5  :  58.5  :  :  24.3  Ibs.  :  x. 
x  =  40.044  Ibs.  (NaCl). 

21.  HCl  of  a  specific  gravity  0/1.2  contains  about  40  per 
cent,  of  the  acid.     This  is  very  strong  commercial  acid.     What 
•weight  of  this  acid  could  be  formed  by  the  HCl  acid  gas  pro- 
duced in  the  reaction  named  in  the  preceding  problem  ? 

If  25  lbs.  =  40  per  cent.,  then  100  per  cent.  =  2.5  times  25  lbs.  =  62  >/s  lbs- 

22.  What  weight  of  hydriodic  acid  (HI)  is  formed  from 
a  drachm  of  iodine  ? 

I  :  HI  :  :  1  dr.  :  x. 
126.8  :  128.8  :  :  1  dr.  :  a. 
.  (Hi). 


IN  CHEMISTRY.  59 

23.  What  weight  of  Glauber  salt  can  be  formed  from  100 
Ibs.  of  oil  of  vitriol?  * 

SOS  :  NaO.SOg  : :  100  Ibs.  :  x. 

40  :  71  : :  100  Ibs.  :  x. 
x  =  177.5  Ibs.  (NaO.S03). 

24.  What  weight  of  S  is  there  in  10  grs.  of  sulphide  of 
hydrogen  ? 

S  :  HS  : :  x  :  10  grs. 

16  :  17  : :  x  :  10  grs. 

z  =  9Vn  grs.  (S). 

25.  How  much  O  is   required  to  change  a  Ib.   of  SO^  to 
SOJ 

S02  :  S03  : :  1  Ib.  :  x. 

32  :  40  : :  1  Ib.  :  x. 

x  =  1 J/4  Ib.  (SO3). 

!V4lb.—  llb.  =  V4  Ib.  (O). 

26.  How  much  phosphorus  in  40  Ibs.  of  phosphate  of  limet 

(See  page  245.)  P  :  3CaO.PO8  : :  <B  :  40  Ibs. 

31  :  155  : :  x  :  40  Ibs. 
x  =  8  Ibs.  (P). 

27.  How  much  P  in  40  Ibs.  of  the  superphosphate  of  lime  ? 

P  :  CaO.PO5  : :  x  :  40  Ibs. 
31 :  99  : :  x  :  40  Ibs. 
x  =  12  "/••  Ibs.  (P). 

28.  How  much  phosphate  of  lime  will  an  oz.  of  P  make  ? 

P  :  3CaO.P06  ::  loz.  :  x. 
31  :  155  : :  1  oz.  :  x. 
x  =  5  oz.  (3CaO.PO6). 

29.  How  many  Ibs.  of  HO  in  186  Ibs.  of  SO^HO  f 

8HO  :  S03.3HO  : :  x  :  186  Ibs. 
27  :  67  : :  x  :  186  Ibs. 
a;  =  74«V67  Ibs.  (HO). 

*  In  this,  as  in  the  other  problems,  the  HO  contained  in  the  acid  and  In 
the  salt  is  neglected,  since  it  is  a  variable  quantity,  and  the  examples  are 
merely  for  practice. 


60  ANSWERS  TO  PRACTICAL   QUESTIONS 

30.  How  much  CO9  is  formed  in  the  combustion  of  I  ton 

of  C? 

C  :  C03  :  :  2000  Ibs.  :  x. 
C  :  22  :  :  2000  Ibs.  :  x. 
x  =  7333  Vs  Ibs.  (COa). 

31.  What  weight  of  S  is  there  in  a  ton  of  iron  pyrites  f 

2S  :  FeS3  :  :  x  :  2000  Iba. 
32  :  60  :  :  x  :  2000  Ibs. 


32.  What  weight  of  copperas  could  be  made  from  500  Ibs. 
of  iron  pyrites  ? 

In  forming  FeO.SO,  from  FeSa  only  one  atom  of  S  is  re- 
quired ;  hence  the  500  Ibs.  of  iron  pyrites  really  contain  but 
366  Vs  Ibs.  of  FeS,  which  will,  at  a  single  reaction,  form  cop- 
peras ;  by  oxydation  from  the  air,  the  remaining  atom  of  S 
would  doubtless  be  used  afterward.  The  problem  might  be 
solved  as  well,  perhaps,  by  taking  either  the  Fe  or  the  S  alone 
as  the  constituent. 

FeS  :  (FeO.S08+7HO)  ::  366  a/s  Ibs.  (FeS)  :  x. 

44  :  139  ::  366  2/3  Ibs.  :  x. 
35=1158.3  Ibs.  (FeO.SO3  +  7HO). 

33.  What  weight  of  H  is  there  in  a  pound  of  heavy  car* 

buretted  hydrogen  ? 

4H  :  C4H<  :  :  x  :  1  lb. 

4  :  28  :  :  x  :  :  1  lb. 

a:  =  V7lb.  (H). 

34.  How  miich  O  would  be  required  to  oxydize  the  metallic 
»opper  which  could  be  reduced  from  its  oxyd  by  passing  over 
it,  when  white-hot,  20  grs.  of  H  gas? 

The  same  amount  of  O  would  be  required  to  oxydize  the 
copper  that  was  taken  from  it  when  it  was  reduced  from  its 
oxyd.  The  H  passing  over  it  when  white-hot  takes  out  its  O 
and  forms  HO.  H  is  always  £  of  the  HO.  The  H  =  20  grs.; 
hence  the  HO  =9  times  20  grs.  =  180  grs.  180  grs.  (HO) 
—  20  grs.  (H)  =  1  60  grs.  (O). 

35.  How  much  O  would  be  required  to  oxydize  the  metallic 
iron  which  could  be  reduced  in  the  same  manner  by  10  grs.  of 
H  %as  ? 


IN  CHEMISTRY.  *>I 

Following  the  same  reasoning  as  in  the  last  problem,  we 
have 

H  =  10  grs. ;  hence  the  HO  =  9  times  10  grs.  =  90  grs. 
90  grs.  (HO)  — 10  grs.  (H)  =  80  grs.  (O). 

}6.    What  weight  of  N  is  there  in  10  Ibs.  of  NH^.HO  f 

N  :  NH8.HO  : :  x  :  10  Ibs. 
14  :  26  : :  x  :  10  Ibs. 
x  =  5  6/i»  Ibs.  (N). 

37.  How  much  KO.  ClOb  would  be  required  to  evolve  suffi- 
cient O  to  burn  the  H  produced  by  the  decomposition  of  ?,  Ibs. 
of  HO? 

f  of  HO  is  O ;  hence  i  Ibs.  of  HO  will  produce,  when  de- 
composed, i$  Ibs.  O.  The  problem  is,  then,  how  much 
KO.C1O,  would  be  required  to  furnish  i$  Ibs.  O  ? 

60  :  KO.C105  :  1.77  Ibs.  :  x. 

48  :  122.5  : :  1.77  Ibs.  :  x. 

a;  =  4.51  Ibs.  (KO.C1O6). 

(If  the  common  fractions  are  used  in  solving  this  problem, 
the  answer  is  4!!  Ibs.) 

38.  How  much  H  must  be  burned  to  produce  a  ton  of 
water? 

H  :  HO  :  *  :  2000  Ibs. 
1:9  : :  x  :  2000  Ibs. 
a;  =  2222/»  Ibs.  (H). 

39.  How  much  S  is  there  in  a  Ib.  of  SO3  f 

S  :  S0a  : :  x  :  1  Ib. 

16  :  32  : :  x  :  1  Ib. 

x  =  Va  H>-  (S). 

40.  Find  how  much  "soda"  is  formed  from  500  Ibs.  of 
salt. 

41.  Find  the  amount  of  Glauber  salt  produced  in  the  first 
step,  with  the  charge  just  named. 

42.  Find  the  amount  of  HCl produced. 

43.  Find  how  much  sulphuret  of  sodium  is  formed  in  the 
second  step. 


02  ANSWERS  TO  PRACTICAL  QUESTIONS 

44.  Find  how  much  sulphuret  of  calcium  is  madt 

45.  Find  how  much  sulphur  could  be  saved  (if  none  were 
lost)  from  the  CaS. 

The  following  reactions  show  the  chemical  changes  which 
take  place  in  the  various  stages : 

(1)    NaCl  +  S03HO  =  NaO.SO, +HC1. 
NaO.SO,  +  2C  =  NaS  +  2COa. 
NaS  +  CaO.C02  =  CaS+NaO.CO,. 

From  the  (i)  reaction  we  find  how  much  Glauber  salt  will 
be  made  from  500  Ibs.  of  common  salt.  To  do  this  we  first 
find  how  much  Na  there  is  in  500  Ibs.  NaCl;  and,  secondly, 
how  much  NaO.SO3  that  amount  of  Na  will  make. 

Na  :  NaCl  : :  x  :  500  Ibs. 
23  :  58.5  : :  x  :  500  Ibs. 
x  =  196  frV  Ibs.  (Na). 
Na  :  NaO.SO,  : :  196  -ft\  Ibs.  :  «. 
23  :  71  ::  196-^  :  x. 
Ibs.  (NaO.SO,).    Ans.  to  tostpnto. 


Na  :  NaO.CO3  : :  196  -ftV  Ibs.  (Na)  :  *. 

23  :  53  :  196  -£fo  Ibs.  :  x. 
Ibs.  (NaO.C03,  "  Soda").    Ans.  to  40th  pnk 

Cl  :  NaCl  : :  x  :  500  Ibs. 
85.5  :  58.5  : :  x  :  500  Ibs. 

a-  =  303 -f^y  Ibs.  (Cl). 
Cl  :  HC1  ::  303 -^Ibs.  :  x. 
85.5  :  36.5  ::  303^  Ibs.  :  *. 

AM.  to  4Sd  pnb. 


Na  :  NaS  ::  196  -j6^  Ibs.  (Na)  :  *. 

23  :  39  ::  196-^rVlbB.  :  x. 
s  333  Va  Ibs.  (NaS).    Ans.  to  4M  proo. 


888  «/•  «».  (NaS)  —  196  -ffr  Ibs.   (Na)  =  136  /ft-  Ibs.  (S).    Ant.  to  I»ro6.  15. 

S  :  CaS  :  :  136  -^f  n».  (s)  •  *• 
x  =  307  Vw  Ibs.  (CaS).    Ans.  to  4Mk  prob 


Itf  CHEMISTRY.  63 

46.  How  many  Ibs.  of  HCl  would  be  required  to  neutralize 
sufficient  carbonate  of  ammonia  to  form  a  30  Ib.  cake  of  sat- 
ammoniac  (NHV  Cl)  ? 

First  find  how  much  Cl  there  is  in  a  30  Ib.  cake  of  sal- 
ammoniac  ;  second,  how  much  HCl  would  contain  that  amount 
of  CL 

Cl  :  NH4C1  : :  x  :  30  Ibs. 
85.5  :  53.5  : :  x  :  30  Ibs. 

x  =  19.9  Ibs.  (Cl). 

Cl  :  HCl  : :  19.9  Ibs.  :  x. 

35.5  :  36.5  : :  19.9  Ibs.  :  x. 

x  =  20.4  Ibs.  (HCl). 

47.  How  much  S  is  there  in  a  ton  of  plaster  (gypsum)  f 

S  :  CaO.SO,  : :  x  :  2000  Ibs. 

16  :  68  : :  x  :  2000  Ibs. 

x  =  470.58  Ibs.  (S). 

48.  How  much  aluminum  is  there  in  a  ton  of  clay  t 

2A1  :  AlaO3.SiO3  : :  x  :  2000  Ibs. 

27.4  :  81.4  : :  x  :  2000  Ibs. 

»  =  673.2  Ibs.  (Al). 

49.  How  much  K  is  there  in  10  Ibs.  of  alum  f 

K  :  (KO.S08+A12O,.3SO,+£1HO)  :  x  :  10  Ibs. 

39  :  474.4  : :  x  :  10  Ibs. 

x  =  .82  Ib.  (K). 

50.  How  much  white-lead  (PbO.COJ  could  be  made  from 
I  Ib.  of  litharge  1 

Pb  :  PbO  : :  x  :  1  Ib. 

103  :  111.6  : :  x  :  1  Ib. 

«  =  .92  Ib.  (Pb)  in  1  Ib.  of  litharge. 

Pb  :  PbO.C02  : :  .92  Ib.  :  x. 

103  :  133  : :  .92  :  x. 
x  =  1.1  Ib.  (PbO.COa). 

51.  How  many  Ibs.  of  C  would  be  required  to  reduce  40 
tons  of  brown  hematite  (-zFe^O^HO)  ? 

In  the  intense  heat  of  the  furnace  the  3 HO  would  be  de- 
composed, and  so  only  sufficient  C  would  be  required  to  burn 


64  ANSWERS  TO  PRACTICAL  QUESTIONS,  &c. 

the  6  atoms  of  O  in  the  2FetO,.     In  40  tons  of  brown  hema- 
tite there  are  34.22  of  the  base. 

6O  :  2Fe2O3  : :  x  :  34.22  tons. 

48  :  160  : :  x  :  34.22  tons. 

x  =  10.26  tons  (O). 

Eight-elevenths  of  COa  is  O  ;  if  10.26  tons  is  -fr,  it  would 
require  3.84  tons  of  C  to  burn  10.26  tons  of  O,  and  thus 
reduce  40  tons  of  hematite. 

52.  In  60  Ibs.  of  heavy  spar  (sulphate  of  baryta}  how  much 

S  is  there  ? 

S  :  BaO.SO3  : :  x  :  60  Ibs. 

16  :  116.5  : :  x  :  60  Ibs. 

x  =  8.2  Ibs.  (S). 

$3.  How  much  alum  can  be  made  from  i  cwt.  of  potash  f 

KO  :  (KO.SOs  -f  AlaO3.3S03+24HO)  :  100  Ib.  :  c. 
47  :  474.4  ::  100  Ibs.  :  x. 
s  =  1009.3  +  Ibs  (alum). 


ANSWERS 

TO  THE  PRACTICAL  QUESTIONS 

IN  THE 

FOURTEEN  WEEKS    COURSE 

IN 

DESCRIPTIVE  ASTRONOMY. 


: .  Did  Tycho  Brake  have  a  telescope  f 
No.     Galileo  invented  the  telescope. 

2.  Suppose  one  should  watch  the  sky,  on  a  winter's  evening, 
from  6  P.  M.  to  6  A.  M. ,  what  portion  of  the  celestial  sphere, 
•would  he  see  ? 

All  that  is  ever  seen  in  his  latitude. 

3.  How  do  we  find  what  proportion    of  the  sun's   heal 
reaches  the  earth  ? 

Calculate  the  surface  of  a  sphere  whose  radius  is  the  dis- 
tance of  the  earth  from  the  sun,  and  then  estimate  what  pro- 
portion of  that  area  the  earth  occupies. 

4.  How  many  real  motions  has  the  sun  ? 

Two.  One  around  its  axis,  and  one  with  the  solar  system 
around  (he  Pleiades. 

5.  How  many  apparent  motions  has  the  sun  ? 

Three..  One  along  the  ecliptic, — its  yearly  motion;  one 
through  the  heavens, — its  daily  motion ;  and  one  N.  and  S. 

6.  How  many  real  motions  has  the  earth  ? 

Three.     One  on  its  axis ;  one  around  the  sun  ;  an<i  i  *h;rd 
its  "wabbling  motion,"  which  causes  Precession. 


66  4.NSWERS  TO  PRACTICAL   QUESTIONS 

7.  Can  any  inferior  planet  have  an  elongation  of '90°  f 
No.     Venus  recedes  only  48°  from  the  sun. 

8.  How  do  we  know  the  heat  of  the  surfs  rays  at  any  planet? 
The  intensity  of  the  heat  and  light  vary  inversely  as  the 

square  of  the  distance. 

9.  Can  yon  give  any  other  proof  than  that  named  in  thf 
book,  of  the  rotundity  of  the  earth  ? 

Aeronauts,  when  at  a  proper  height,  can  distinctly  see  the 
curving  form  of  the  earth's  surface. 

10.  In  what  way  is  the  force  which  acts  on  a  spinning-top 
opposite  to  that  which  produces  precession  (p.  125)  ? 

Gravity^acting  on  the  top,  tends  to  draw  C  P  (Fig.  34)  ./>*"» 
the  perpendicular.  The  attraction  of  the  sun,  acting  on  the 
bulging  mass  of  the  earth's  equator,  tends  to  draw  C  P  toward 
the  perpendicular. 

1 1 .  Why  is  the  Tropic  of  Cancer  placed  where  it  is  ? 
Because  it  is  the  farthest  place  north  where  the  sun  is  evei 

seen  directly  overhead. 

12.  Why  is  the  Tropic  of  Cancer  so  called? 

When  named,  the  sun  was  probably  in  that  constellation  at 
the  time  of  the  summer  solstice.  Now,  owing  to  the  preces- 
sion of  the  equinoxes,  the  sun  is  in  the  constellation  Gemini, 
and  to  be  exact,  it  should  be  called  the  Tropic  of  Gemini.  It 
is  still,  however,  the  sign  Cancer,  as  before.  The  same  reason- 
ing applies  to  the  Tropic  of  Capricorn,  which  is  now  in  the 
constellation  Sagittarius. 

13.  In  Greenland ',  at  what  part  of  the  year  will  the  mid- 
night sun  be  seen  due  north  ? 

At  the  summer  solstice. 

14.  How  do  we  know  that  the  moon  has  little  if  any  atmos- 
phere? 

Because  when  the  moon  occults  a  star,  there  is  no  refraction 
of  the  star's  true  place. 

15.  When  is  the  moon  seen  high  in  the  eastern  sky  in  the 
afternoon,  lotig  before  the  ?un  sets  ? 


IN  DESCRIPTIVE  ASTHOXOMY  67 

During  the  second  quarter  before  it  comes  into  opposition. 

1 6.  Why  is  the  Ecliptic  so  called  ? 
Because  eclipses  always  occur  within  it. 

17.  Why  is  it  that  the  sun  in  summer  shines  on  the  north 
side  of  some  houses  both  at  rising  and  setting,  but  in  'winter 
never  does  f 

Since  at  the  summer  solstice  the  sun  rises  and  sets  north  of 
the  E.  and  W.  points,  it  will  rise  and  set  on  the  north  side  of 
a  house  which  stands  exactly  N.  and  S.  At  the  winter  solstice 
the  sun  rises  and  sets  S.  of  the  E.  and  W.  points 


TABLE  OF  THE  MINOR  PLANETS. 


Wo. 

Name. 

Date  of  Discovery. 

Discoverer. 

Siderml 
Revolution 
(Days.) 

1 

Cores  

1801,    January      1 

Piazzi     . 

1680 

2 

Pallas  

1802,    March        28 

Olbers 

1682 

3 

J'ino 

1804     Sept            1 

Harding 

1596 

4 

Vesta  

1807,    March       29 

Gibers?  

1326 

5 

A^tnea  

1845,    December  8 

Hencke 

1512 

6 

Hebe  

1847,    July            1 

Hencke       .  . 

1379 

7 

Iris 

1847     August      13 

Hind 

1346 

8 

Flora  

1847,    October     18 

Hind  

1193 

9 

Metis  

1848,    April         25 

Graham  .  . 

1346 

10 

Hygieia  . 

1849,    April          12 

Gasparis 

2043 

11 

1850,    May           11 

Luther  

1403 

12 

Victoria  

1850,    Sept.         13 

Hind    .  .. 

1303 

13 

Egeria.    .  . 

1850,    Nov.            2 

Gasparis 

1511 

14 

Irene 

1851,    May           IS) 

Hind 

1519 

15 

Kunomia  

1851,    July           29 

Gap  par  is  

1570 

16 

Psyche       .  .     . 

1852,    March       17 

Gasparis 

1828 

17 

Thetis 

1852,    April         17 

Luther 

1421 

18 

M  elpomene  

1852,    June          24 

Hind  

1271 

19 

Fortuua  

1852,    August      22 

Hind     ...     . 

1393 

20 

Massalia.  . 

1852,     Sept.          19 

Ga-'paris 

1365 

21 

Lutetia 

1852     Nov            15 

Goldschmidt 

1388 

22 

Calliope  

1852,    Nov.          16 

Hind  

1813 

23 

Thalia 

1852,    Dec            15 

Hind 

1556 

24 

Themis 

1853,    April           5 

Gasparis 

2036 

25 

Phocaea  

1853,    April           7 

Chacornac  

1358 

26 

Proserpina  .  .    . 

1853,    May            5 

Luther 

1580 

27 

Euterpe 

1853,    Nov             8 

Hind 

1313 

28 

Bellona  

1854,    March         1 

Luther  

1692 

29 

Amphi  trite  

1854,    March         1 

Marth 

1492 

80 

Urania 

1854,    July           22 

Hind 

1329 

31 

Euphrosyne  

1854,    Sept.           1 

Ferguson  

2048 

32 

Pomona    

1854,    October     26 

Goldschmidt  '.  .  .  .  . 

1521 

33 

Polyhymnia 

1854,    October    28 

Chacoruac 

1778 

34 

Circe  

1855,    April           6 

Chacornac  

1609 

35 

Leucothea  

1855,    April         19 

Luther       

19U3 

36 

Atalanta          .  .  . 

1855,    October      5 

Goldschmidt    . 

16(>4 

37 

Fides 

1855     October      5 

Luther 

1569 

38 

Leda   

1856,    January    12 

Chacornac  

1657 

39 

Laetitia 

1856,    February    8 

Chacornac 

1684 

40 

Harmonia 

1856     March       31 

Goldschmidt 

1247 

41 

Daphne  .  .  . 

1856,    May           22 

Goldschmidt  

1C81 

42 

Isis 

1856,    May           23 

Pogson            .  .  . 

1392 

43 

Ariadne 

1857     April         15 

Poison 

1195 

44 

Nysa  

1857,    May           27 

Goldschmidt  

1379 

45 

Eugenia  

1857,    .Tune          27 

Goldschmidt 

1638 

46 

Hestia  

1857,    August      16 

Pogrson 

1470 

47 

Aglaia 

1857     Sept           15 

1788 

4S 

Doris  

1857,    Sept.          19 

Goldschmidt  

20^3 

49 

Pales 

1857,    Sept.          19 

Goldschmidt  ... 

I'^S 

50 

1857,    October      4 

Ferguson 

1576 

51 

1858     January    22 

1338 

52 

Europa       .... 

1858,    February    4 

Goldschmidt  

1993 

5:i 

Calypso 

1858,    April            4 

Luther 

1548 

54 

1858     Sept.          10 

Goldschmidt 

1634 

55 

Pandora     

1858,    Sept.          10 

Searle  

1674 

TABLE  OF  THE  MINOR  PLANETS. 


No. 

Name. 

Date  of  Discovery. 

i 
Discoverer. 

Sidercul 
Revolution 
(Days.) 

56 

Melete* 

1857     Sept            9 

Goldschmidt  

152C 

57 

16£'9     Sept           22 

Luther  

204.) 

58 

1860     March       24 

Luther 

1615 

59 

Elpis 

lf->60     Sept           12 

Chacornac  

1634      • 

60 

Echo    

18tiO,    Sept.         15 

Ferguson  

1353      ' 

61 

1860     Sept            9 

Golaschmidt 

1902 

62 

Erato 

I860'    Sept           14 

Forster  and  Lesser. 

2023      ' 

63 
64 

Ausonia  

1861,    February  10 
1861      March         4 

Gasparis  

Tempel 

1355  '  | 
1601 

65 

Cybele 

18(51     March         8 

Teinpel  

2311 

66 

Maia 

1S61     April           9 

Tut,tle  

1588 

67 

Asia 

1861,    April          17 

Pogson  

1375 

68 

Leto 

1861      April          29 

Luther  

1695 

69 

Igiil     April          29 

Schiaparelli  

1893 

70 

71 

Panopea  
Niobe 

186!,    May             5 
1861      August      13 

Goldschmidt  
Luther  

1542 
1671 

72 

Feronia  

1861,    May           29 

Peters  and  Safford. 

1245 

73 

Clytie 

1862     April           7 

Tattle 

1590 

74 

1862'    August      29 

Tempel 

1691 

75 

186/    Sept          22 

Peters       

1594 

76 

Freia 

1862,    October    21 

d'Arrest  

2080 

77 

FritT^a 

1862,    Nov.          12 

Peters     

1596 

78 

Diana 

1863     March        15 

Luther      .  .     . 

1554 

79 

1863     Sept           14 

Watson 

1399 

80 
81 

Sappho  

1864,    May             2 
1864     Sept          30 

Pogson  

Tempel. 

1270 
Ifi93 

8'i 

Alcmene 

1864,    Nov.          27 

Luther  

1659 

83 

1865     April          5<6 

Gasparis  

l:;8t 

84 

Clio       

1865,    August      26 

Luther  

1330 

85 

lo 

1865,     Sept.          19 

Peters  

1583 

86 

1866     January      4 

Tietjen    

1983 

87 

Sylvia 

1866     May            16 

Poijson 

2384 

88 

Thisbe 

1866,    June          15 

Peters  

1675 

89 

Julia 

1866     August        6 

Stephan 

1472 

90 

Antiope  

1866,    Ocfober    11 

Luther  

^031 

91 

^jjViiia 

1866,    Nov.            4 

Mephan    

1495 

92 

Uudina  

1867,    July            7 

Peters  

2086 

93 

Minerva  . 

1867,    August      24 

Watson  

1669 

94 

1867     Sept.           6 

Watson  

2050 

95 

1867     Nov           23 

Luther 

1964 

96 

Jj>le 

1868,    February  17 

Coggia  

1950 

97 

Clotho 

1868     February  17 

Tempel 

1592 

98 

lanthe 

1868     April          18 

Peters 

1607 

99 
100 

Dike  
Hecate 

1868,    May           28 
1868     July           11 

Borelly  
Watson 

1892 

101 

1868     August      15 

Watson 

1508 

lOv 

M  i  riam 

1868,    August      22 

Peters  

1587 

103 

Hera 

1868      Sept.            7 

Watson 

1622 

104 

Clymene 

1868,     Sept.          ]3 

Watson  

2071 

105 

Artemis 

1868,    Sept.          16 

Watson       .       .     .. 

1341 

106 

Dione 

1868     October     10 

Watson 

2092 

107 

Camilla     . 

1868,    Nov.          17 

Pogson      

108 

Hecuba 

1869,    April           2 

Luther 

2104 

109 

Felicitas 

1869     Oct              9 

Peters 

1615 

•Goldschmidt  at  first  believed  it  to  be  Daphne  (41),  but  Schubert  finding  its  perioa 
different,  called  it  Pseudo-Daphne.  It  was  not  seen  from  1857  to  1861,  wLea  Lullw 
rediscovered  it,  and  named  it  Mdete. 


The  numerical  order  is  that  adopted  by  the  authority  of  the  Berlin  Epfacmeru. 


TABLE  OF  THE  MINOR  PLANETS. 


No. 

Name. 

Date  of  Disr:overy. 

Discoverer. 

Log.  a.* 

110 

Lydia. 

1870     April        19 

Borelly 

0  4371°G 

111 

Ate  

1870,    August    14 

Peters  

0  413183 

112 

Iphigenia  . 

1870,    Sept.        19 

Peters  

0  386324 

113 

Amalthea 

1»71      March      12 

Luther 

0  375971 

114 

Cassandra 

18  Tl     July         23 

Peters 

0  427422 

115 

1871,     August      6 

Watson  

0  376540 

116 

Sirona 

1871,     Sept.          8 

Peters    . 

0  441912 

117 

118 

Lomia  
Peitho 

1871,    Sept.        12 
1872,    March      15 

Borelly  

Luther        .   .  . 

0.475643 

0  386977 

119 

1872,     Anril          3 

Watson  

0.410304 

120 

Lachesis  

1872      April        10 

Borelly  

0  495810 

121 

1872     May          12 

Watson 

0  538%7 

122 

Gerda           .   .. 

1872,    July         31 

Peters.             

0  508118 

123 

Brunhilda     

1872     July         31 

Peters. 

0  430151 

124 

Alcesto 

1872      \ivu«t    23 

Peters 

0  419063 

125 

1872,     Sept         11 

Prosper  Henry 

0  48219 

126 

1872     Nov.          5 

Paul  Henry 

0  386778 

127 

1872,    Nov.           5 

Prosper  Henry.  .  . 

0.44377     ; 

128 

1872,     Nov.         25 

Watson 

129 

Antigone. 

1873     Feb            5 

Peters    .  .  . 

0  457822 

130 

Electra  

1873,    Feb.         17 

Peters  

*  Log.  a  i 
sun  as  unit 


logarithm  of  inyjr  seinlaxis  of  orbit,  taking  the  earth  s  distance  from  th« 


SIMPLE  DIRECTIONS 

TO  A  BEGINNER 

FOR 

PERFORMING  THE  EXPERIMENTS 

IN  THE 

FOURTEEN  WEEKS    COUKSE 

IK 

CHEMISTRY. 

(OLD    NOMENCLATURE.) 


[The  large  figures  refer  to  the  paere  of  the  Chemistry,  and  the  small  ones  to 
the  number  of  the  experiment.  Read  for  additional  directions,  Chemistry, 
pp.  235-248,  and  new  edition,  pp.  245-267.] 


11.  I.  Put  as  much  chlorate  of  potash  (potassic  chlorate) 
as  will  lie  upon  the  point  of  a  knife-blade,  and  half  as  much 
sulphur,  into  the  mortar.  Grind  them  slowly  with  the  pestle 
until  the  ingredients  are  thoroughly  mixed  and  distributed 
over  the  bottom  of  the  mortar.  Hold  the  mortar  so  that  the 
loose  particles  cannot  fly  into  your  eyes,  nor  the  flame  burn 
your  clothes,  and  then  grind  heavily  with  the  pestle,  when 
rapid  detonations  will  ensue.  The  mixture  will  last  for  days. 
After  use,  clean  out  the  mortar  carefully  for  other  experi- 
ments. The  powder  can  be  wrapped  with  paper  into  a  hard 
pellet  and  exploded  on  an  anvil  by  a  sharp  blow  from  a  ham- 
mer. Sometimes  small  bits  of  phosphorus  are  used  instead 
of  sulphur.  Great  care  is  then  necessary,  as  the  particles  of 
burning  phosphorus  are  apt  to  fly  to  some  distance. 

12.  i.  Two  teaspoonfuls  of  common  carbonate  of  soda  and 
one  of  tartaric  acid  should  be  dissolved  separately  in  a  wine- 
glass of  water.  On  being  poured  together  in  a  larger  glass, 
they  will  violently  effervesce.  Use  a  glass  large  enough  to 


72  DIRECTIONS  FOR  PERFORMING 

prevent  any  running  over  upon  the  table.  Neatness  in  ex- 
periments is  essential  to  perfection,  and  often  to  success. 

15.  i.  The  cabbage  solution  is  made  by  steeping  p.urple  cab- 
bage leaves  in  water.  A  little  lemon-juice  or  vinegar  will  turn 
it  to  a  bright  red,  and  a  little  of  the  potash  solution  to  a  deep 
green.  Add  a  little  alcohol  to  the  red  solution,  to  keep  it 
from  freezing,  and  bottle  it  for  use.  Dissolve  a  little  of  the 
dry  litmus  in  water,  filter  and  bottle  it.  These  are  to  be  used 
in  testing  the  alkalies  and  acids.  Dissolve  also  a  stick  of  the 
potash  in  water,  filter  and  bottle.  Fill  two  test-tubes  nearly 
full  of  water ;  color  one  with  the  cabbage  and  the  other  with 
the  litmus  solution.  Add  a  few  drops  of  the  potash  solution 
and  of  the  sulphuric  acid  alternately  to  each.  The  color  can 
be  changed  at  pleasure. 

Take  a  small  bit  of  tubing,  and  heating  the  ends  in  the 
flame  of  the  spirit-lamp  (the  greatest  heat  is  near  the  tip  of 
the  flame),  seal  up  the  opening.  This  will  be  useful  to  dip 
into  the  acid  or  alkali,  as  it  will  remove  a  drop  more  readily 
than  by  dropping  from  the  bottle. 

2O.  Pulverize  an  ounce  of  the  potassic  chlorate  very  care- 
fully; stir  in  it  one-fourth  of  its  weight  of  the  black  oxyd  of 
manganese  and  place  the  mixture  in  the  copper  retort,  at- 
tach the  tubing  and  gas-bag  as  shown  in  the  figure  of  p. 
234 ;  or  in  the  Florence  flask,  attaching  a  delivery  tube,  as 
shown  in  figure  on  p.  20.  The  glass  tubing  may  be  heated 
in  the  flame  of  the  alcohol-lamp  «and  bent  to  the  desired 
shape,  or  it  can  be  broken  into  short  lengths  by  simply  start- 
ing the  break  in  the  tube  by  a  mere  scratch  with  a  three-cor- 
nered file  and  then  connecting  the  pieces  of  glass  tubing  with 
a  short  bit  of  the  small  rubber  tubing,  as  in  the  figure  on 
p.  20.  The  gas  may  be  passed  off  from  the  gas-bag,  or  di- 
rectly from  the  retort  into  the  pneumatic  cistern,  C,  across 
which  is  placed  a  jhelf  perforated,  to  permit  the  gas  to  bubble 
up  into  the  receiver,  J.  The  pneumatic  cistern  may  consist 
of  a  tub  of  water.  The  bottles  for  collecting  the  gas  are  sunk 
into  the  water  until  filled,  inverted,  and  then  lifted  up  on 
the  shelf,  carefully  keeping  the  lower  edge  of  the  bottle  be- 
neath the  water.  A  large  tin  pan,  without  any  shelf,  may  be 
used  as  a  cistern  by  filling  the  bottles  full  of  water  in  a  deep 


EXPERIMENTS  IN  THE  CHEMISTRY.  73 

pail,  and  then  slipping  a  plate  underneath  each  one,  as  shown 
in  the  second  figure  on  p.  22,  leaving  enough  water  on  the 
plate  to  cover  the  edge  of  the  bottle ;  it  may  then  be  lifted 
out  and  placed  in  the  cistern.  In  the  same  way  the  bottles, 
when  filled  with  gas,  may  be  remc  ved  and  kept  for  use.  Gas 
may  be  passed  from  one  bottle  to  another  by  inverting  one 
over  the  other  beneath  the  water  in  the  pneumatic  cistern, 
or  in  a  large  pail,  when  the  gas  will  bubble  up  from  the  lower 
one  into  the  upper  one. 

Apply  the  heat  to  the  glass  retort  very  carefully  at  first, 
holding  the  lamp  in  the  hand  and  moving  it  around  so  that 
the  flame  may  strike  all  the  lower  part  of  the  flask,  and  thus 
expand  it  uniformly.  Be  careful  also  that  there  is  no  draft  of 
cold  air  to  strike  against  the  heated  retort.  With  the  cop- 
per retort  no  care  of  this  kind  is  necessary.  When  the  gas 
ceases  to  come  off,  remove  the  stopper  or  lift  the  end  of  the 
tube  out  of  the  water;  otherwise,  as  the  retort  cools  and  a 
vacuum  is  formed,  the  water  in  the  cistern  will  set  back  into 
the  flask,  and,  if  of  glass,  will  break  it.  An  ounce  of  the  salt 
will  make  over  six  quarts  of  oxygen  gas.  When  the  retort  is 
oartly  cooled,  pour  in  some  warm  water  to  dissolve  the  residu- 
um, which  may  then  be  poured  out  and  the  retort  drained  and 
set  away  for  future  use.  In  order  to  test  the  purity  of  the 
materials,  and  thus  avoid  any  danger  of  an  explosion,  place  a 
little  of  the  mixture  for  making  oxygen  in  an  iron  spoon  and 
aeat  it  over  the  spirit-lamp.  If  the  gas  passes  off  quietly,  no 
langer  need  be  apprehended. 

22.  i.  The  experiment  with  the  candle  can  be  performed 
•nost  strikingly  by  filling  a  common  fruit-jar  with  nitrogen 
vsee  page  32)  and  another  with  oxygen.  The  covers  will  pre- 
5erve  the  gases  until  wanted  for  use.  The  covers  may  then 
be  laid  loosely  on  top  cf  the  jars,  and  the  lighted  candle 
passed  quickly  from  one  jar  to  the  other.  It  will  be  ex- 
anguished  in  one  and  relighted  in  the  other.  With  care,  it 
may  be  passed  and  repassed  a  dozen  times.  This  strikingly 
illustrates  the  difference  between  oxygen  and  nitrogen.  Test 
the  carbonic  acid,  in  this  as  in  all  similar  experiments,  with 
the  blue  litmus  and  the  green  cabbage,  or  a  slip  of  blotting- 
paper  wet  with  the  litmus  solution.  A  few  drops  of  the  solu- 


74  DIRECTIONS  FOR  PERFORMING 

tion  may  be  poured  into  the  jar,  and  then  the  jar  shaken,  so 
as  to  permit  the  water  to  absorb  the  gas.  The  candle  may  be 
simply  stuck  upon  the  end  of  a  bent  wire,  but  it  is  much 
neater  to  have  the  tinsmith  fit  a  little  cup  for  its  reception,  as 
shown  in  the  figure. 

2.  The  worn-out  watch-springs  which  can  be  obtained 
gratis  of  any  jeweller,  may  be  easily  straightened  by  draw- 
ing them  between  the  fingers.  If  the  end  of  each  spring  be 
heated  and  then  pounded  with  a  hammer  on  any  smooth 
hard  surface,  the  temper  may  be  thoroughly  drawn  and  the 
edge  sharpened.  Make  a  slit  with  a  knife  in  the  side  of  a 
match,  :nto  which  insert  the  edge  of  the  spring.  Take  a 
piece  of  zinc  or  tin  large  enough  to  cover  the  mouth  of  the 
jar  containing  the  oxygen,  and  make  a  hole  through  it  with 
a  nail.  Pass  the  other  end  of  the  spring  through  this  hole, 
and  then  through  a  thin  cork.  The  spring  is  now  ready  for 
burning.  The  metal  cover  will  prevent  the  flame  from  roming 
out  of  the  jar  and  burning  one's  hand,  and  the  cork  will  hold 
the  spring  in  its  place.  When  the  match  is  ignited,  and  then 
lowered  into  the  jar  of  oxygen,  the  spring  should  not  reach 
more  than  half-way  to  the  bottom,  and  should  be  pushed 
down  as  it  burns.  If  a  specie-jar  be  used,  do  not  fill  it  quite 
full  of  gas,  as  a  little  water  left  in  the  bottom  will  prevent  the 
melted  globules  of  iron  from  breaking  the  glass. 

23.  I.  If  brimstone  be  used  in  this  experiment,  and  it  fails 
to  light  readily,  pour  upon  it  a  few  drops  of  alcohol,  and  then 
ignite  it. 

2.  If  you  have  not  a  deflagrating  spoon  to  contain  the  phos- 
phorus, one  may  be  readily  extemporized.     Hollow,  a  small 
piece  of  chalk  and  attach  it  to  a  wire,  which  may  then  be  se- 
cured to  a  metal  top,  as  in   the  case   of   the    watch-spring. 
This  need  not  be  pushed  down  into  the  jar  as  the  burning 
progresses.    ,  At  the  close  of  the  experiment,  test  for  the  acid 
formed  in  the  combustion.     The  fumes  are  very  disagreeable, 
and  should  not  be  inhaled  or  allowed  to  escape  into  the  room. 

3.  If  a  piece  of  bark  charcoal  be  ignited,  and  then  lowered 
into  a  jar  of  oxygen,  it  will  deflagrate  with  bright  scintilla- 
tions. 

31.    I.  Put  in  an  evaporating-dish  a  little  starch;  cover  if 


EXPERIMENTS  IN  TUK  CHEMISTRY.  75 

with  water  in  which  a  few  crystals  of  iodide  of  potassium  have 
been  dissolved,  and  heat.  Stir  the  liquid,  to  prevent  lumps. 
When  cooked,  immerse  in  the  paste  slips  of  blotting-paper. 
Use  while  moist.  Be  careful  not  to  heat  the  glass  tube  too 
hot,  lest  the  ether  vapor  may  ignite.  Keep  the  jar  well  rilled 
with  vapor  by  frequently  shaking  it.  Lower  into  the  ozone  a 
bit  of  silver-leaf  moistened  with  water ;  it  will  quickly  crumble 
into  dust,  the  oxyd  of  silver. 

34.  i.  To  make  the  iodide  of  nitrogen,  cover  a  few  scales 
of  iodine  with  strong  aqua  ammonia.  After  standing  for  a 
half-hour,  pour  off  the  liquid  and  place  the  brown  sediment  in 
small  pieces  on  bits  of  broken  earthenware  to  dry.  This  will 
require  several  hours.  They  may  then  be  taken  to  the  class- 
room very  carefully  and  exploded  by  a  slight  touch  of  a  rod, 
or  even  a  feather. 

37.  I.  For  making  NOB  a  special  apparatus  is  necessary 
for  complete  success.  The  Florence  flask  may,  however,  be 
used,  and  the  heat  of  the  spirit-lamp  will  be  sufficient.  The 
fumes  may  be  caught  in  the  evolution  flask,  which  is  kept 
cool  by  a  towel  frequently  wet.  When  the  retort  is  partially 
cooled,  at  the  conclusion  of  the  process,  pour  in  a  little  warm 
water,  to  dissolve  the  sulphate  of  potash,  otherwise  the  retort 
may  break  by  the  crystallization  of  the  salt. 

2.  Mix  equal  parts  of  nitric  acid  and  oil  of  vitriol  (perhaps 
a  teaspoonful  of  each),  and  pour  the  mixture  on  hot  finely- 
powdered  charcoal,  or  on  a  little   oil   of  turpentine.     It  will 
be  oxydized  with  almost  explosive  violence.     This  should  be 
performed  out  of  doors. 

3.  Bits  of  tin  may  be  obtained  of  any  tinsmith.     Put  them 
in  a  tumbler  and  nearly  cover  them  with  the  NO6.     In  using 
copper,  the  apparatus  shown  on  page  39  is  excellent.     The 
acid   may  be  turned  in  gradually  through  the  funnel  tube. 
Before  putting  in  the  acid  pour  into  the  flask  warm  water  to 
cover  the  lower  end  of  the  funnel  tube,  which  should  nearly 
reach  the  bottom  of  the  flask.     When  a  jar  is  filled  with  the 
NO,  it  may  be  lifted  out  of  the  water  and  inverted,  when  the 
NO4  will  pass  off  in  blood-red  clouds.     If  the  jar  be  left  in 
the  cistern  and  one  edge  be  lifted  so  as  to  admit  a  bubble  of 
air,  red  fumes  will  fill  the  jar.     By  standing  a  moment  the 


7  6  DIRECTIONS  tfOlt  PERFORMING 

water  will  absorb  the   red  vapor.     This  process   can  be   re- 
peated several  times  with  the  remaining  gas. 

4O.  I.  The  finely-powdered  sal-ammoniac  and  lime  may 
be  mixed  in  an  evaporating-dish.  The  escaping  ammonia 
should  be  tested  with  a  glass  rod  or  tube  wet  with  hydrochloric 
acid. 

2.  Heat  a  little  aqua  ammonia  in  the  Florence  flask.  Col- 
lect the  vapor  in  an  inverted  bottle,  to  which  is  fitted  a  cork 
and  tube,  with  the  inner  extremity  drawn  to  a  fine  point  over 
the  spirit-lamp.  Insert  the  cork,  and  then  plunge  the  bottle 
into  a  vessel  of  water.  The  water  which  passes  in  first  will 
absorb  the  gas  so  quickly  as  to  make  a  partial  vacuum,  into 
which  the  water  will  rush  so  violently  as  to  produce  a  minia- 
ture fountain. 

42.  i.  In  making  H,  the  directions  given  on  pages  236-7 
should  be  carefully  observed.  For  purifying  the  gas  a  solu- 
tion of  potash  should  be  placed  in  the  flask  d  (page  42).  If  a 
junk  bottle  be  used  the  acid  should  be  added  slowly,  as  the 
heat  generated  is  liable  to  break  the  bottle.  Pour  the  water 
into  the  flask  a  until  the  lower  end  of  the  funnel  is  covered, 
before  adding  the  acid.  The  flow  of  gas  may  be  regulated 
by  additions  of  acid,  as  may  be  wanted.  One  part  of  acid  to 
ten  or  twelve  of  water  will  liberate  the  gas  very  rapidly.  If 
it  comes  off  very  fast,  the  liquid  is  liable  to  froth  over.  The 
philosopher's  lamp,  page  237,  is  very  interesting.  The  jet 
may  be  a  straight  glass  tube  drawn  to  a  fine  point  over  the 
spirit-lamp.  Large  glass  tubes  or  the  beaks  of  broken  re- 
torts, held  over  this  flame,  will  produce  the  singing  tones, 
though  not  as  well  as  the  apparatus  figured  in  the  book.  The 
tone  may  be  regulated  by  the  size  of  the  flame,  z.  <?.  the  rapid- 
ity with  which  the  gas  comes  off,  the  size  of  the  jet  as  well  aa 
the  length  and  size  of  the  tubes.  The  H  can  be  collected 
over  the  pneumatic  cistern,  or,  since  it  is  lighter  than  air,  in 
inverted  bottles.  As  soon  as  the  bottles  are  turned  right  side 
up  the  gas  will  escape.  To  measure  the  H  and  O  for  the 
"  mixed  gases,"  a  receiver,  with  a  stop-cock  on  top,  which 
may  be  connected  by  rubber  tubing  with  the  gas-bag,  is  very 
useful.  The  oxygen  may  be  passed  directly  into  the  gas-bag, 
however,  as  on  page  234,  until  it  is  about  one-third  full,  when 


EXPERIMENTS  IN  THE  CHEMISTRY.  77 

the  bag  may  be  removed  and  attached  to  the  hydrogen  ap- 
paratus to  be  filled. 

5O.  I.  In  lieu  of  a  small  crucible,  fill  a  common  tobacco- 
pipe  with  crystals  of  blue  vitriol,  and  heat  them  over  the 
lamp  or  in  a  common  fire  until  the  water  of  crystallization  is 
expelled.  Alum  may  be  rendered  anhydrous  in  the  same 
manner. 

56.  i.  Small  paste-diamonds  may  be  obtained  of  a  jewel- 
ler, to  illustrate  the  forms  of  cutting  the  diamond. 

6O.  i .  Place  a  filtering  paper  in  the  glass  funnel,  and  in  it 
a  couple  of  ounces  of  bone-black  or  finely-powdered  charcoal. 
Filter  through  it  water  colored  with  ink,  litmus,  or  any  other 
impurities.  In  pouring  the  liquid  into  the  filter  hold  a  glass 
rod  against  the  edge  of  the  pouring  vessel,  so  as  to  direct  the 
stream  into  the  funnel.  The  funnel  may  be  placed  in  the 
nozzle  of  a  bottle,  but  must  not  fit  closely.  A  bit  of  wood  or 
a  thread  inserted  between  the  stem  of'  the  funnel  and  the 
nozzle  will  leave  an  opening  sufficient  for  the  egress  of  the  air. 

64.  i.  Break  some  marble  into  small  bits ;  place  them  care- 
fully in  the  evolution-flask,  and,  inserting  the  cork  and  tube, 
pour  in  HC1  slowly.  The  gas,  on  account  of  its  weight,  may 
be  passed  directly  into  a  bottle  or  jar. 

2.  Lower  a  lighted  candle  into  a  jar  of  the  gas,  or,  lowering 
the  candle  into  an  empty  jar,  pour  the  gas  into  the  jar,  as  if  it 
were  water.     Test  the  acid  with  litmus  paper. 

3.  Place  a  piece  of  lime  as  large  as  an  egg  in  a  pint  of  wa- 
ter; let  it  stand    overnight;  pour  off  the  clear  liquid — it  is 
lime-water.     Place  a  little  in  a  tumbler  and  breathe  through  it 
by  means  of  a  tube,  or  pass  a  current  of  CO,  from  the  evolu- 
tion-flask until  the  liquid,  at  first  milky,  clears. 

4.  Breathe  through  a  tube  into  an  empty  bottle.      Lower 
into  it  a  lighted  candle — it  will  be  immediately  extinguished. 
Pour  in  some  lime-water,  shake  it  thoroughly  and  it  will  be- 
come milky. 

5.  Twist  a  wire  around  the  neck  of  a  small  wide-mouthed 
vial,  to  answer  as  a  bucket.     Lower  it  by  the  wire  into  a  jar 
of  COa,  our  ideal  well  foul  with  the  gas.     Raise  it  again,  and 
test  for  the  CO,  by  means  of  a  lighted  match.     The  bucket 
will  be  found  to  be  full  of  the  gas. 


78  DIRECTIONS  FOR  PERFORMING 

6.  Fill  a  jar  with  hydrogen,  and  in  a  similar  way  dip  the 
gas  downward  and  burn  it  over  a  lamp.     This  shows  in  a  very 
striking  manner  the  difference  between  H  and  CO3  in  respect 
to  specific  gravity.     The  one,  we  see,  is  dipped  upward,  the 
other  downward. 

7.  Balance  a  large  paper  bag  or  box  on  a  delicate  pair  of 
scales,  or  in  any  simple  manner  one's  ingenuity  may  suggest. 
Empty  into  the  box  a  large  jar  of  CO3,  and  the  box  will  quickly 
descend. 

8.  Arrange    little   wax-tapers  in  a  wooden    or    pasteboard 
trough,  as  on  page  65.     Light  them,  and  then  pour  in  at  the 
top  a  bottle  of  carbonic  acid  gas.     If  the  proper  slant  is  given 
to  the  trough,  all  the  candles  will  be  extinguished. 

72.  i.  Olefiant  gas  may  be  made  by  heating  in  the  flask  one 
part,  by  measure,  of  alcohol  and  two  parts  of  sulphuric  acid. 
Pass  it  through  a  smution  of  potash,  as  shown  on  page  88,  and 
then  collect  in  the  gas-bag.  Fit  a  piece  of  glass  tubing,  drawn 
to  a  fine  point  at  one  end,  to  the  stop-cock  of  the  gas-bag  by 
means  of  a  bit  of  the  rubber  tubing.  On  turning  the  stop- 
cock and  forcing  out  the  gas  it  may  be  ignited,  when  it  will 
burn  with  a  clear  white  light. 

2.  Fill  a  tall  jar  one-third  full  of  olefiant  gas,  and  the  re- 
mainder with  chlorine  gas.      On   lighting,   the    mixture  will 
burn  with  a  dense  cloud  of  smoke.     HC1  is  the  product  of  the 
combustion. 

3.  Mix  with   oxygen  ana  explode  in  soap-bubbles.     It  pro- 
duces a  greater  noise  even  than  the  "  mixed  gases."     Great 
care  must  be  taken  not  to  let  the  light  approach  the  gas-bag 
containing  the  mixture. 

4.  Fit  a  large  test-tube  with  a  cork  and  a  piece   of  glass 
tubing,  drawn  to  a  fine  point  at  the  outer  end.      Fill  the  tub 
with  fine  dry  pine-shavings.     On  heating,  the  gases  from  the 
wood  will  pass  off,  and  can  be  ignited  at  the  jet- tube.     The 
test-tube  can  be  held  by  a  strip  of  twisted  paper  or  wire. 

5.  At  the  close  of  the  ist  exp.  perform  the  one  figured  on 
page  79.      A  small  piece  of  wire-gauze,  4  or  6  inches  square, 
for  this  purpose  can  be  purchased  of  any  tinsmith.     If  you  do 
not  force  the  gas  out  too  rapidly,  you  will  be  able  to  burn  it 
on  either  side  of  the  gauze  at  pleasure. 


EXPERIMENTS  IN  THE  CHEMISTRY.  79 

79.  Place  on  top  of  the  gauze  a  bit  of  camphor-gum.  Ig- 
nite it,  and  the  flame  will  not  pass  through  to  the  lower  side. 
Then  ignite  on  the  lower  side,  and  extinguish  the  flame  on  the 
upper  side. 

77.  The  carbonic  acid  of  a  burning  candle  may  be  passed 
through  lime-water  in  the  following  manner.  Take  a  bottle 
arranged  with  tubes,  as  in  the  middle  one  shown  in  the  figure 
on  page  87.  From  the  tall  tube  at  the  left  suspend  a  glass 
funnel  with  the  stem  coupled  to  the  tube  by  means  of  a  piece 
of  rubber  tubing.  Place  under  this  funnel  a  burning  candle. 
Partly  fill  the  bottle  with  lime-water.  Then  placing  the  mouth 
to  the  right-hand  tube,  draw  out  the  air  from  the  bottle.  This 
makes  a  draft  over  the  candle,  and  draws  its  invisible  smoke 
through  the  funnel,  down  the  long  tube,  and  up  through  the 
lime-water,  which  soon  becomes  milky. 

SO.  The  compound  blow-pipe  with  gasometers,  as  shown  on 
page  238,  is  the  most  serviceable.  If  gas-bags  are  used,  the 
one  for  hydrogen  should  be  twice  the  size  of  the  one  for  oxy- 
gen. A  board  should  be  laid  on  each  bag,  upon  which  weights 
may  be  placed,  when  ready  for  use,  so  as  to  force  out  the  gas 
steadily.  Turn  the  stop-cock  so  that  the  H  will  pass  out 
twice  as  fast  as  the  O.  Always  ignite  the  H  first,  and  then 
turn  on  the  O  slowly  until  the  best  effect  is  produced.  If  gas- 
ometers are  used,  press  the  inner  receivers  down  to  the  bottom, 
and  then  pour  in  water  till  it  reaches  nearly  the  top.  The  rub- 
ber pipes  may  then  be  attached  to  the  hydrogen  or  oxygen 
apparatus,  and  the  gases  passed  directly  into  the  gasometers. 
Proper  pressure  is  produced,  when  the  jet  is  to  be  ignited,  by 
unloosing  the  strings  from  the  inner  receivers,  and  thus  taking 
off  the  "  lift"  of  the  weights  which  equipoise  them.  Additional 
pressure  is  secured  by  bearing  down  upon  the  receivers.  All 
the  metals  burn  in  the  blow-pipe  flame  with  their  character- 
istic colors.  Narrow  slips  should  be  prepared  for  this  purpose. 
A  mirror,  and  a  cup  for  holding  the  chalk,  are  necessary  to 
show  the  lime-light.  A  piece  of  hard  chalk  or  lime,  whittled 
to  about  the  size  of  a  pencil,  may  be  held  in  the  flame  to  illus- 
trate the  principle. 

87.  Put  in  the  flask  two  ounces  of  common  salt  and  an 
ounce  and  a  half  of  black  oxyd  of  manganese.  Pour  on 


8o  DIRECTIONS  FOR  PERFORMING 

enough  water  to  reduce  the  mixture  to  a  thin  liquid.  Shake 
the  flask  until  the  whole  interior  is  moistened.  Insert  the  cork 
and  delivery-tube ;  the  middle  bottle  shown  in  the  figure  is  not 
necessary.  Fill  the  pneumatic  cistern  with  warm  water,  using 
just  as  small  a  quantity  as  possible,  since  water  absorbs  the  gas. 
Pour  in  an  ounce  of  the  oil  of  vitriol  through  the  funnel-tube,  or 
directly  at  the  nozzle,  by  removing  the  ground  stooper,  if  a 
kind  of  flask  be  used  which  has  one.  The  gas  will  come  ofi 
at  once,  even  before  the  heat  is  applied.  Collect  the  gas  in 
bottles  and  use  directly,  if  convenient,  otherwise  put  corks  in 
them  and  rub  the  nozzles  well  with  tallow.  Pass  the  gas 
through  cold  water,  as  shown  on  page  88,  or  more  simply, 
through  a  tumbler  of  water.  This  will  form  chlorine  water, 
which  should  be  bottled  and  kept  in  a  dark  place. 

2.  Fill  a  test-tube  nearly  full  of  pure  rain  or  snow  watei, 
and  let  fall  into  it  a  drop  or  two  of  the  nitrate  of  silver  solu- 
tion. A  drop  of  HC1  will  form  a  cloudy  white  precipitate. 

91.  i.  Place  on  a  clean  white  dish  a  few  scales  of  iodine 
and  a  bit  of  phosphorus  as  large  as  a  pea.  It  will  soon  ignite. 

2.  Fill  three  test-tubes  nearly  full  of  soft  water.      Pour  in 
one  a  few  drops  of  a  solution  of  bichloride  of  mercury,  into 
the  second    of  sugar  of  lead,  into  the  third  of  subnitrate  of 
mercury  (formed  by  pouring  NO6  on  mercury).     Add  to  each 
of  these  a  few  drops  of  the  solution  of  iodide  of  potassium. 
The  first  especially  will  produce  a  brilliant  color  (iodide  of 
mercury) ;  the  rapid  change  from  yellow  to  red  is  very  marked. 
On  continuing  to  add  the  iodide  of  potassium,  the  red  precip- 
itate will  be  dissolved  and  disappear. 

3.  Make  an  additional  quantity  of  the  iodide  of  mercury, 
as  in  the  2d  exp.      Let  it  settle.      Pour  off  the  liquid,  and 
then    spread  the  sediment   on  a  piece  of  heavy  card-board, 
making  a  red  spot  as  large  as  a  silver  dollar.     Dry  it  care- 
fully.     Then  heat  very  strongly,   when  it  will    turn    yellow. 
Rub  over  the  yellow  spot  the  point  of  a  knife  several  times, 
bearing  on  very  firmly,  and  a  red  mark  can  be  seen.    Lay  away 
the  paper  for  a  day  or  two,  and  the  red  color  will  spread  ovei 
the  whole  spot. 

4.  Dissolve  a  few  scales  of  iodine  in  fifteen  or  twenty  times 
its  bulk  of  alcohol.      Pour  a  few  drops  of  this  solution  on  a 


EXPERIMENTS  IN  THE  CHEMISTRY.  Si 

freshly  -cut  potato  or  apple.     Blue  specks  will  show  the  pres- 
ence of  starch. 

96.  I.  Melt  a  quantity  of  sulphur,  either  the  flowers  or 
brimstone,  in  a  test-tube.  It  is  at  first  thick  and  dark-colored, 
but  after  continued  heating  becomes  thin  and  dark-colored. 
Pour  it  now  into  water  and  it  will  form  an  elastic  gum,  which 
can  be  moulded  into  any  desired  form. 

2.  Heat  a  piece  of  brimstone  in  a  test-tube.     After  a  little 
the  sulphur  will  sublime  and  collect  in  the  upper  part  of  the 
tube  as  flowers  of  sulphur. 

3.  Fill   a  cup   with   brimstone   and   melt   it  with  a  gentle 
heat.      Set  it  aside  to  cool.      When  a  crust  has   formed  on 
top,  break  it  and  pour  out  the  liquid  contents.     If  the  cup 
be  broken,  the  bottom  will  be  found  covered  with  crystals  of 
sulphur. 

1OO.  Place  in  the  evolution-flask  half  an  ounce  of  sulphuret 
of  iron.  Cover  this  with  water,  and  then  pour  in  oil  of  vitriol 
through  the  funnel  until  the  gas  comes  off  freely.  It  may 
be  passed  through  a  glass  of  cold  water.  This  solution  must 
be  bottled  and  closely  corked.  The  gas  may  be  tested  di- 
rectly; see  page  137. 

1O2.  i.  Cover  a  stick  of  phosphorus  with  dry,  fine-pow- 
dered charcoal.  It  will  soon  ignite. 

2.  Put  in  a  vial  half  an  ounce  of  sulphuric  ether  and  a  half- 
dozen  pieces  of  phosphorus  not  larger  than  grains  of  wheat. 
Thoroughly  shake  and  then  set  away.     Repeat  the  shaking 
often.     When  the  phosphorus  is  dissolved,  pour  a  little  of  the 
solution  on  the  hands,  and  when  briskly  rubbed  together  in  a 
dark  place  they  will  glow  with  a  ghostly  light. 

3.  Pour  some  of  the  solution  on  a  lump  of  loaf-sugar.    Drop 
this  in  hot  water,  when  the  ether  will  catch  fire. 

4.  Place  in  a  wine-glass  a  few  crystals  of  chlorate  of  potash 
and  a  small  bit  of  phosphorus.     Fill  the  glass  nearly  full  of 
water.     By  means  of  a  funnel-tube,  pour  a  little  oil  of  vitriol 
to  the  bottom  of  the  glass.     A  violent  deflagration  will  imme- 
diately take  place,  and,  in  a  daik  room,  flashes  of  green  light 
will  be  seen. 

119.  Cut  off  three  or  four  inches  of  magnesium  ribbon,  and 
holding  one  end  with  a  pair  of  pincers,  thrust  the  ot-bf-r  into 


82  DIRECTIONS  FOE  PERFORMING,  ETC. 

the  flame  of  the  spirit-lamp.  The  metal  will  almost  instantly 
ignite,  when  it  may  be  removed  and  held  up  to  the  view  of  the 
class  until  the  Mg  is  consumed. 

124.  To  make  a  saturated  solution  of  alum,  drop  crystals 
of  the  salt  into  boiling  water,  until  a  drop  of  the  liquid  taken 
out  on  the  end  of  a  glass  rod  and  put  on  a  bit  of  glass  will 
crystallize  as  soon  as  it  cools. 

134.  Fill  a  test-tube  nearly  full  of  water.  Pour  in  it  a  few 
drops  of  the  solution  of  sulphate  of  copper.  Add  ammonia, 
and  a  blue  precipitate  will  be  formed.  Notice  the  change  from 
green  to  blue.  The  sulphate  of  copper  may  be  readily  made 
for  this  experiment  by  covering  a  copper  cent  with  dilute  oil  of 
vitriol.  This  experiment  may  be  made  to  show  the  divisibility 
of  matter  by  weighing  the  cent,  then  seeing  what  proportion  of 
the  whole  solution  you  use,  and  then  experiment  to  find  what 
quantity  of  water  can  be  taken  and  yet  have  the  blue  color 
perceptible  in  the  ammonia  test. 

185.  Fill  a  test-tube  one-sixth  full  of  sweet  oil,  add  a  little 
ammonia,  and  nearly  fill  with  water.  The  constituents  remain 
separate.  Shake  thoroughly,  and  they  will  combine,  forming 
a  thin,  soapy  liquid.  Add  an  acid,  and  they  will  dissolve  part- 
nership at  once. 


SUGGESTIONS. 

Melted  snow,  or  very  clear  rain-water,  will  answer  the  place 
of  distilled  water  in  making  solutions,  &c.,  for  experiments. 
Whenever  corks  leak  gas  they  may  be  wrapped  with  thin  strips 
of  wet  paper  to  make  them  fit  more  tightly,  or  the  entire 
nozzle  may  be  smeared  with  tallow,  or  covered  with  sealing- 
wax,  if  heat  is  not  used.  In  that  case  a  little  plaster  of  paris 
may  be  wet  up  and  quickly  applied.  The  experimenter  will 
find  a  retort-stand  for  holding  the  retorts,  a  test-tube  holder,  a 
set  of  tin  cork-borers,  several  Florence  flasks  of  different  sizes, 
the  copper  retort  for  making  oxygen,  and  the  gas-bag,  with 
its  tubing  and  connectors,  almost  indispensable.  After  these, 
the  compound  blow-pipe  is  of  the  greatest  value.  A  few  drops 
of  a  solution  of  magenta  (i  dr.  in  a  gill  of  HO)  will  color  the 
water  beautifully,  and  add  to  the  effect  of  certain  experiments. 


KEY 


TO 


CHEMISTRY  ip  PHYSIOLOGY, 


ANSWERS 

TO     THE 

PRACTICAL  QUESTIONS  AND  PROBLEMS 

IN     THE 

FOURTEEN    WEEKS    IN    CHEMISTRY, 

REVISED    EDITION, 
WITH     NEW     NOMENCLATURE. 


[The  large  figures  refer  to  the  page  of  the  Chemistry^  and  the  small  ones 
to  the  number  of  the  Question^ 


24. — i.  In  a    2$-lb.   sack  of  common  salt,  how  many 
pounds  of  the  metal  sodium  ? 

Na  =  23   =  atomic  weight  of  the  given  element. 
NaCl  =  58.5  =  molecular  weight  of  the  compound. 

x  =  weight  of  the  given  element. 
25  Ibs.  =       "  "    compound. 

Na  :  NaCl  :  :  x  :  25  Ibs. 
23  :   58.5    :  :  x  :  25  Ibs. 
58.5  x  =  575  Ibs. 

x  =  9rVT  Ibs.  (Na). 

2,  In  14  Ibs.  of  iron  rust  (Fe2O3),  how  much  O? 

Os  =  48  =  atomic  weight  of  the  given  element. 
FeaO3  =  160  =  molecular  weight  of  the  compound. 

x  =  weight  of  the  given  element. 
14  Ibs.  =       w  u   compound. 

O8  :  FeaOs  :  :  x  :  14  Ibs. 
48  :  160  :  :  x  :  14  Ibs. 
160  x  —  672  Ibs. 
x  =  4£  Ibs.  (O). 


86  ANSWERS  TO  PRACTICAL   QUESTIONS 

3.  How  much  S  is  there  in  2  Ibs.  0/SO2  ? 

S  =  32  =  atomic  weight  of  the  given  element. 
SO  a  =  64  =  molecular  weight  of  the  compound. 

x  =  weight  of  the  given  element. 
2  Ibs.  =        "  u    compound. 

S  :  SOa  :  :  x  :  2  Ibs. 
32  :    64     :  :  x  :  2  Ibs. 
644  =  64  Ibs. 
x  =  i  lb.  (S). 

4.  How  much  S  is  there  in  2  Ibs.  oj  H2SO4  ? 

S  :  H2SO«  :  :  x  :  2  Ibs. 
32  :       98        :  :  jr  :  2  Ibs. 
98  x  =  64  Ibs. 
JT  =  SJ  lb.  (S). 

5.  .#bw  w^  O  is  there  in  5  Ibs.  o/HNO3  ? 

O3  =  48  =  atomic  weight  of  the  given  element. 
HNO3  =  63  =  molecular  weight  of  the  compound. 

x  =  weight  of  the  given  element. 
S  Ibs.  =       "  "    compound. 

O,  :  HNO3  :  :  x  :  5  Ibs. 
48  :      63       :  :  x  :  5  Ibs. 
63  x  =  240  Ibs. 
x  =  3tf  Ibs.  (O). 

6.  How  much  H  is  there  in  6  Ibs.  of  HC1  ? 

H  :  HCl  :  :  x  :  6  Ibs. 

i  :   36.5    :  :  JJT  :  6  Ibs. 

36.5  x  =  6  Ibs. 

•*  =  A0.  =  I!  lb.  (H). 


K2O  tfw/;/  be  made  from  3  /Ar.  ^/  K? 

K,  :  KaO  :  :  3  Ibs.  :  x. 

78  :     94     :  :  3  Ibs.  :  x. 

78  x  —  282  Ibs. 

*  =  3r8s  Ibs.  (K.O). 

40.  —  I.  Are  all  acids  sour  ? 

(See  Chemistry,  page  22,  note,  and  also  page  xia) 


IN  CHEMISTRY.  87 

2.  What  is  the  difference  between  an  -ate,  an  -ite,  and  an 
-ide  compound? 

An  -ate  compound  is  a  union  of  an  -ic  acid  with  a  base  ; 
an  -ite  compound  is  a  union  of  an  -ous  acid  with  a  base; 
and  an  -ide  compound  is  a  union  of  two  elements,  a 
binary  compound.  EXAMPLES. — Iron  sulphate,  FeSO4  ; 
calcium  sulphite,  CaSO3  ;  potassium  chloride,  KC1. 

3.  Why  does  not  canned  fruit  decay  ? 
Because  the  O  of  the  air  is  excluded. 

4.  Where  is  the  higher  oxide  formed,  at  the  forge  or  in 
the  pantry  ? 

(See  Chemistry,  page  33,  note.) 

5.  Why  is  the  blood  red  in  the  arteries  and  dark  in  the 
veins  ? 

When  specimens  of  venous  and  of  arterial  blood  are 
subjected  to  chemical  examination,  the  differences  pre- 
sented by  their  solid  and  fluid  constituents  are  found  to 
be  very  small  and  inconstant.  As  a  rule,  there  is  rather 
more  water  in  arterial  blood,  and  rather  more  fatty  mat- 
ter. But  the  gaseous  contents  of  the  two  kinds  of  blood 
differ  widely  in  the  proportion  which  the  carbonic  acid 
gas  bears  to  the  oxygen  ;  there  being  a  smaller  quantity 
of  oxygen  and  a  greater  quantity  of  carbonic  acid,  in 
venous  than  in  arterial  blood.  And  it  may  be  experi- 
mentally demonstrated  that  this  difference  in  their  gaseous 
contents  is  the  only  essential  difference  between  venous 
and  arterial  blood.  For  if  arterial  blood  be  shaken  up 
with  carbonic  acid,  so  as  to  be  thoroughly  saturated  with 
that  gas,  it  loses  oxygen,  gains  carbonic  acid,  and  acquires 
the  hue  and  properties  of  venous  blood  ;  while,  if  venous 


88  ANSWERS  TO  PRACTICAL   QUESTIONS 

blood  be  similarly  treated  with  oxygen,  it  gains  oxygen, 
loses  carbonic  acid,  and  takes  on  the  color  and  properties 
of  arterial  blood. — HUXLEY'S  Lessons  in  Physiology. 

6.  Why  do  we  need  more  oxygen  in  winter  than  in  summer  ? 

Because  there  is  a  brisker  fire  going  on  in  our  cor- 
poreal stoves. 

7.  Which  would  starve  sooner ;  a  fat  man  or  a  lean  one  1 

(See  Chemistry,  page  35,  note.) 

A  superabundance  of  flesh,  in  a  time  of  scarcity,  is 
taken  up  by  the  absorbents  and  thrown  into  the  circula- 
tion, thus  supplying  the  place  of  food  in  nourishing  the 
body. 

8.  How  do  teamsters  warm  themselves  by  slapping  their 
hands  together  ? 

To  produce  the  motion,  additional  O  is  supplied,  and 
increased  oxidation  is  the  result.  This  liberates  heat  to 
warm  the  body.  Besides,  the  blood  sets  to  the  arms  and 
the  general  circulation  becomes  more  rapid.  This  extra 
supply,  both  by  its  presence  and  the  friction  of  the  swiftly 
moving  currents,  furnishes  heat,  and  thus  raises  the  tern 
perature  of  the  body. 

9.  Could  a  person  commit  suicide  by  holding  his  breath  ? 

Respiration  is  entirely  independent  of  consciousness, 
as  is  seen  in  sleep,  coma,  etc.  It  may  be  interrupted  fot 
a  few  minutes,  but  no  effort  of  the  will  can  enable  one  to 
hold  his  breath  until  life  is  extinct.  The  desire  for  O, 
the  besoin  de  respirer,  or  the  respiratory  sense,  as  it  is 
called,  becomes  at  last  so  great  that  the  strongest  reso- 
lution yields  the  struggle. 


IN  CHEMISTS  Y.  89 

10.  Why  do  we  die  when  our  breath  is  stopped1} 

"  In  asphyxia  it  is  difficult  to  say  which  destroys  life, 
the  absence  of  oxygen  or  the  presence  of  carbonic  acid." 
— FLINT.  There  is  an  absence  of  oxygen,  so  essential 
to  every  vital  operation,  and  also  an  accumulation  of 
carbonic  acid  *  in  the  system. 

1 1.  Why  do  we  breathe  so  slowly  when  we  sleep  ? 

(See  Chemistry,  page  35.) 

Because  so  little  muscular  action  is  going  on  in  the 
body. 

12.  How  does  a  cold-blooded  animal  differ  from  a  warm- 
blooded one  ? 

In  the  imperfection  with  which  the  blood  is  oxygenated. 
The  lungs  are  often  of  small  capacity,  and  loose  texture, 
and  are  sometimes  wanting  entirely.  In  reptiles  a  por- 
tion of  the  blood  is  not  sent  to  the  heart,  and  hence  in 
the  vessels  there  is  a  mixture  of  arterial  and  venous 
blood.  The  breathing  is  therefore  slow,  the  motions  are 
languid,  and  there  is  little  heat. 

13.  Why  does  not  the  body  burn  out  like  a  candle? 

Because  it  is  renewed  by  the  processes  of  assimilation 
and  nutrition  as  rapidly  as  it  is  destroyed  by  the  waste 
of  oxidation.  Whenever  the  former  are  in  excess  we 
gain  flesh,  when  the  latter,  we  grow  poor. 

14.  Do  all  parts  of  the  body  change  alike? 

*  This  gas  remains  fixed  in  the  blood-corpuscles,  and  renders  them  inca- 
pable of  furnishing  any  oxygen  to  the  system.  CO  is  a  deadly  poison, 
because  it  clings  to  the  disks  more  tenaciously. 


9°  ANSWERS  TO  PRACTICAL   QUESTIONS 

The  rate  of  change  varies  with  the  amount  of  oxida- 
tion, and  that  depends  on  the  use  of  the  organ.  The 
right  arm  of  the  blacksmith  must  be  transformed  much 
more  rapidly  than  the  left. 

15.  What  objects  would  escape  combustion  ? 

Burnt  bodies,  i.  e.,  those  which  are  already  combined 
with  oxygen. 

1 6.  How  much  oxygen  can  be  obtained  from   6   oz.   of 
KClOo  ? 

0:,  :  KC103  :  :  x  :  6  oz. 

48  :     122.5     •  :  x  '•  6  oz. 

122.5  x  —  288  oz. 

x  =  2.35  oz.  (O). 
Or  (see  Chemistry,  page  28),  £&   x  6  oz.  =  2  £?s  oz.  (O). 

17.  How  much  KC1O3  would  be  needed  to  produce  2 
Ibs.  0/O? 

O,  :  KC1O3  :  :  2  Ibs.  :  x. 

48  :     122.5     :  :  2  ^bs.  :  jr. 

48  x  =  245  Ibs. 

x  =  SiV  Ibs.  (KC1O,). 

1 8.  How  much   KC1  would  be  formed  in  preparing  i 
Ib.  o/O 

(See  Chemistry,  page  28,  diagram.) 

If  i  Ib.  is  sW  of  a  compound,  what  are  ^f  ? 
Ans.  -V<f  Ibs.  =  ifc|  Ibs.  (KC1). 

19.  Name  a  substance  from  which  the  O  can  be  set  free 
by  the  stroke  of  a  hammer. 

Potassium  chlorate. 

20.  Name  one  from   which   it  is   liberated  with  great 
difficulty. 

Sand,  carbonic  anhydride.     (See  C/tem,,  p.  98,  note.) 


IN  CHEMISTRY.  91 

21.  Is  .it  probable  that  all  the  elements  have  been  dis- 
covered ? 

(See  Key,  page  49,  Question  i.) 

22.  Is  heat  PRODUCED  by  oxidation  ? 

(See  Chemistry,  pages  36  and  100.^ 

All  forms  of  force — electricity,  heat,  muscular  energy, 
chemical  attraction,  gravitation,  etc.,  are  now  considered 
as  movements  of  molecules ;  the  particles  being  in  con- 
tinuous, undulatory  motion,  the  swiftness  and  width  of 
the  vibrations  determining  the  character  of  the  force. 
These  forces  are  interchangeable,  but  cannot  be  created 
or  annihilated,  increased  or  diminished. 

23.  What  is  the  difference  between  dynamic  and  potential 
force? 

A  potential  force  is  one  that  is  latent ;  a  dynamic,  one 
that  is  sensible.  The  former  is  hidden  ;  the  latter  is  in 
full  action.  Potential  force  is  a  weight  wound  up,  a  loaded 
gun,  a  river  trembling  on  the  brink  of  a  precipice,  a  giant 
waiting  the  word,  an  engine  with  the  valve  closed. 
Dynamic  force  is  the  weight  falling,  the  river  tumbling, 
the  giant  striking,  the  engine  flying  along  the  track. 

24.  Why  does  running  cause  panting? 

As  soon  as  we  begin  to  perform  any  unusual  exercise, 
we  commence  breathing  more  rapidly — showing  that,  in 
order  to  do  the  work,  we  need  more  O  to  unite  with  the 
food  and  muscles.  In  very  violent  labor,  as  in  running, 
we  are  compelled  to  open  our  mouths,  and  take  in  deep 
inspirations  of  oxygen. 

25.  How  does  O  give  us  strength  ? 

(See  Chemistry,  page  35.) 


9 2  ANSWERS  TO  PRACTICAL   QUESTIONS 

Our  muscles,  as  well  as  the  food  from  which  they  are 
formed,  consist  of  complex  molecules,  and  the  tension  of 
the  forces  is  very  great.  When  they  oxidize,  the  potential 
force  becomes  a  dynamic  one. 

26.  Does  the  plant  PRODUCE  force'! 

(See  Chemistry,  page  100.) 

It  only  gathers  up  the  solar  force. 

27.  If 'we  burn  an  organic  body  in  a  stove,,  it  gives  off 
heat ;  in  the  body  it  produces  also  motion.     Explain. 

The  force  set  free  by  the  oxidation  of  the  muscles,  and 
food  within  the  body  is,  by  the  principle  of  the  correla- 
tion of  forces,  converted  into  muscular  energy. 

28.  In  preparing  N   a  thin,  white  cloud  remains  in  the 
Jar  for  a  long  time.      What  is  it  ? 

Probably  an  antozone  cloud. 

49. — i.  How  could  you  detect  any  free  O  in  ajar  0fN  ? 

By  passing  into  the  jar  a  bubble  of  NO,  and  watching 
for  the  production  of  the  red  fumes  of  NO2. 

2.  How  would  you  remove  the  product  of  the  test? 
By  letting  the  jar  stand  over  water. 

3.  In  the  experiment  shown  in  Fig.  1 1,  why  is  the  gas  red 
in  the  flask,  but  colorless  when  it  bubbles  up  into  the  jar  ? 

Because  the  NO2  formed  by  the  air  present  in  the  flask 
is  absorbed  by  the  H2O  in  the  pneumatic  tub. 

4.  How  much  H3N  can  be  obtained  from  3  Ibs.  of  sal- 
ammoniac  ? 


IN  CHEMISTRY.  93 

(z).     H,N  :  H4N,C1  :  :  x  :  3  Ibs. 
17  :      53.5       :  :  x  :  3  Ibs. 
53-5  •*"  =  5*  Ibs. 

x  =  m  lb.  (H3N). 

(2).  From  the  formulae  it  is  seen  that  any  amount  of  sal-ammoniac  will 
yield  |5f  its  weight  of  ammonia:  hence,  3  Ibs.  will  give  3  Ibs.  x  ||f  =  fgf 
lb.  (H,N). 

5.  flow  much  H2O  will  be  formed  in  the  process'} 

By  examining  the  reaction  given  in  the  Chemistry  ',  page 
48,  it  will  be  seen  that  \  of  the  H  in  each  molecule  of 
H4N,C1  goes  to  form  H2O.  Hence,  find  (i)  how  much 
H  there  is  in  3  Ibs.  of  sal-ammoniac,  and  (2)  how  much 
H2O  would  be  formed  by  J-  that  amount  of  H. 

(i)    H4  :  H4N,C1  :  :  x  :  3  Ibs. 
4  :      53-5       :  :  *  V  3  Ibs. 
53.5  jr  =  12  Ibs. 

x  =  T<&  lb.  (H). 

(2)    T%V  lb.  +  4  =  T^T  lb.    T§T  lb.  x  9  *  =  T°5V  lb.  (HaO). 

6.  ^?z£/  wwr/^  CaO  will  be  needed? 


Find  (i)  how  much  O  there  is  in  -ffe  lb.  of  H2O  ; 
and  (2)  how  much  CaO  would  be  needed  to  furnish  that 
amount  of  O. 

(i)    TS5V  lb.  x  I  *  =  T«587-  lb.  ;  hence,  there  are  ^r  lb.  of  O  in  the  water  pro- 
duced. 

(2)     O  :  CaO  :  :  TVr  lb.  :  x. 
16  :     56     :  :  T4587  lb.  :  x. 
16  x  =  -\9oV8-- 

x  -  1.57  +  Ibs.  (CaO). 

7.  In  separating  N,  how  much  air  will  be  needed  to  fur- 
nish a  gallon  of  the  gas  ? 

About  f  of  the  atmosphere  is  N  :  hence,  J  of  a  gallon 
of  common  air  would  be  required  to  furnish  one  gallon 

of  N. 

*  See  Chemistry  \  page  24. 


94  ANSWEB8  TO  PRACTICAL   QUESTIONS 

8.  How  much  N2O  can  be  made  from  i  Ib.  of  ammonium 
nitrate  ? 

N8O  :  H4N,NO3  :  :  x  :  i  Ib. 

44  :          80  :  :  x  :  i  Ib. 

80  x  =  44  Ibs. 

x  =  ii  Ib.  (N20). 


9.  ^?a/  #zz/^  «//r*f  #«V/  <:#«  be  formed  from  50  /&r.  of 
sodium  nitrate  (NaNO3)  1 

Find  (i)  how  much  N  there  is  in  50  Ibs.  of  sodium 
nitrate  (Chili  saltpetre),  and  (2)  how  much  HNO3  could 
be  made  from  that  amount  of  N. 

(1)  N  :  NaN03  :  :  x  :  50  Ibs. 
14  :        85        :  :  x  :  50  Ibs. 

85  x  —  700  Ibs. 
x  =  8rV  Ibs.  (N). 

(2)  N  :  HNO.  :  :  8fy  Ibs.  :  x. 
14  :       63       :  :  8TV  Ibs.   :  x. 

14  x  =  518,4  Ibs. 

x  =  37Ty  Ibs.  (HN03). 

10.  What  causes  flesh  to  decompose  so  much  more  easily 
than  wood  ? 

It  is  partly  owing  to  the  greater  complexity  of  its  mole- 
cule, and  partly  to  the  presence  of  the  fickle  N. 

11.  If  a  tuft  of  hair  be  heated  in  a  test  tube,  the  liquid 
formed  will  turn  red  litmus-paper  blue.     Explain. 

Ammonia  is  formed  by  the  decomposition  of  the  hair, 
and  this  acting  on  the  red  litmus-paper  turns  it  blue. 

12.  Why  should  care  be  used  in  opening  a  bottle  of  strong 
H3N  in  a  warm  room  ? 

The  volatile  gas  sometimes  drives  out  the  liquor  am- 
moniae  with  great  force. 


7^  CHEMISTRY.  95 

13.  What  weight  of  N  is  there  in  10  Ibs.  <7/"HNO3  ? 

N  :  HNO3  :  :  x  :  to  Ibs. 
14  :       63        :  :  jr  :  10  Ibs. 
63  .*•  =  140  Ibs. 
-r  =  2g  Ibs.  (N). 

14.  ./iftw  much  sal-ammoniac  would  be  required  to  make 
2  Ibs.  <7/-H3N? 

HSN  :  H4N,C1  :  :  2  Ibs.  :  or. 
17  :      53.5       :  :  2  Ibs.  :  x. 
17  x  =  107  Ibs. 

x  =  6T5f  Ibs.  (H4N,C1). 

15.  Give  illustrations  of  the  replacement  of  the  H  in  an 
acid  by  a  metal. 

(See  Chemistry,  page  44,  note  ;  page  51,  reaction  ;  and  page  128,  note.) 

1  6.    What  is  the  difference  between  liquid  ammonia  and 
liquor  ammonia  ? 

Liquid  ammonia  is  the  gas  condensed  into  a  liquid  by 
cold:  liquor  ammonias  is  a  solution  of  the  gas  in  H2O. 

63.  —  i.    Why,  in  filling  the  hydrogen  gun,  do  we  use  5 
parts  of  common  air  to  2  of  H,  and  only  one  part  of  '  O  to 

2 


Because  the  air  is  only  \  oxygen,  and  hence  5  parts  of 
common  air  are  equivalent  to  i  part  oxygen. 

2.  Why  are  coal  cinders  often  moistened  with  H2O  before 

using  ?  (See  Chemistry,  page  57,  note.) 

The   H2O  being  decomposed  by  the   heat  of  the  fire 
increases  the  combustion. 

3.  What  injury  may  be  done  by  throwing  a  small  quan- 
tity 0/HzOon  afire  ? 

"  No  more  heat  is  produced  by  the  action  of  the  H2O, 


96  AN8WEES  TO  PRACTICAL   QUESTIONS 

but  it  is  in  a  more  available  form  for  communicating  heat. 
The  steam  in  contact  with  incandescent  charcoal  is 
decomposed — the  O  going  to  the  C  to  form  CO2,  and 
the  H  being  set  free.  If  the  C  is  abundant,  and  the  heat 
high,  the  CO2  is  also  decomposed,  and  double  its  volume 
of  CO  formed.  The  inflammable  gases,  H  and  CO, 
mingled  with  the  hydrocarbons  always  produced,  are 
ignited,  making  the  billows  of  flame  which  sweep  over 
a  burning  building." — S.  P.  SHARPLES. 

4.  Why  does  the  hardness   of  water  vary  in   different 
localities  ? 

The  hardness  of  the  water  will  necessarily  vary  with 
the  solubility  of  the  minerals  in  different  localities. 

5.  What  causes  the  variety  of  minerals  in  the  ocean  ?     Is 
the  quantity  increasing  ? 

The  ocean  contains  the  washings  of  the  land.  Every 
mineral  soluble  in  water  is  borne  to  the  sea.  The  quan- 
tity of  mineral  matter  in  the  ocean  would  therefore  seem 
to  be  increasing,  yet  there  is  a  compensation  in  the  return 
to  the  soil,  of  guano,  marine  plants,  and  fish,  which  are 
driven  on  shore  by  winds  and  waves,  or  carried  by  the 
industry  of  man. 

Analysis  of  sea-water  (Schweitzer) : 

Water 963-74 

Sodium  chloride 28.05 

Potassium  chloride .76 

Magnesium  chloride 3-66 

Magnesium  bromide .02 

Magnesium  sulphate 2.29 

Calcium  sulphate i-4° 

Calcium  carbonate -03 

Iodine traces 

Ammonia traces 


IN  CHEMISTEY.  97 

6.  Is  there  not  a  compensation  in  the  sea-plants,  fish,  etc., 
which  are  washed  back  on  the  land  ? 

(See  Answer  to  Question  5.) 

7.  Since  "  all  the  rivers  flow  to  the  sea"  why  is  it  not 
full? 

Because  of  the  constant  evaporation  from  its  surface. 

8.  What  is  the  cause  of  the  tonic  influence  of  the  sea 
breeze  ? 

There  are  traces  of  certain  minerals  which  probably 
give  to  the  sea  breeze  a  bracing  influence.  The  air  from 
the  ocean  is  also,  doubtless,  highly  ozonized.  Persons 
with  delicate  lungs,  therefore,  find  the  sea  breeze  too 
corrosive.  In  England,  rheumatic  and  other  inflammatory 
diseases  are  more  abundant  near  the  coast  than  inland. 

9.  When  fish   are  taken   out  of  the  water,  and  thus 
brought  into  a  more  abundant  atmosphere,  why  do  they  die  ? 

Fish  inhale  O  through  the  fine  silky  filaments  of  their 
gills.  When  a  fish  is  drawn  out  of  H2O,  these  dry  up, 
and  it  is  unable  to  breathe,  although  it  is  in  a  more 
plentiful  atmosphere  than  it  is  accustomed  to  enjoy. 

10.  Do  all  fish  die  when  brought  on  land? 

(See  Key,  page  51,  Question  15.) 

11.  What  weight  of  water  is  there  in  100  Ids.  of  sodium 
sulphate  (Na2SO4,ioH3O),  or  Glauber's  salt1} 

ioHaO  :  Na2SO4,ioH2O  :  :  x  :  zoo  Ibs. 
180  :  322  :  :  x  :  100  Ibs. 

322  x  —  18000  Ibs. 

x  =  55.9  Ibs.  (H..O). 

5 


9  AN8WE&8  TO  PRACTICAL   QUESTIONS 

12.  What  weight  of  water  in  a  ton  of  alum  (KA1,2SO4, 
i2H2O)? 

iaH2O  :  KA1,2SO«,  i2H2O  :  :  x  :  2000  Ibs. 
216  :  474-5  '.  :  x  \  2000  Ibs. 

474.5  x  =  432000  Ibs. 

x  —  910.4  Ibs.  (HaO). 

13.  How  much  water  would  it  require  to  furjiish  enough 
H  to  change  5  Ibs.  of  nitric  anhydride  to  nitric  acid? 

Find  (i)  how  much  HNO3  could  be  made  from  5  Ibs. 
•  of  N2O5  (see  Chemistry,  page  44,  note);  (2)  how  much 
H2O  is  contained  in  that  amount  of  HNO3.  The  differ- 
ence between  the  weight  of  the  nitric  anhydride  and  that 
of  the  nitric  acid  will  show  the  amount  of  water  required 
to  furnish  the  H. 

(i).    N2O5  :  2(HNO.)  :  :  5  Ibs.  :  x. 
108  :        126        :  :  5  Ibs.  :  x. 
108  x  —  630  Ibs. 

x  =  5.833  Ibs.  (HNO3). 

(i).    5-833  Ibs.  (HNO3)  -  5  Ibs.  (NaO.)  =  .833  Ib.  (HaO). 

14.  How  does  the  air  purify  running  water? 

The  O  contained  in  the  air  absorbed  by  the  H2O 
oxidizes  the  organic  substances,  which  are  the  most 
dangerous  impurities. 

15.  What  is  the  action  of  potassium  permanganate  as  a 
disinfectant  ? 

It  gives  up  its  O  to  oxidize  the  organic  impurities. 

1 6.  Why  does  lime  sometimes  soften  hard  water  when 
added  to  it  ? 

(See  Key^  page  50,  Question  4.) 

17.  What  weight  of  H  can  be  obtained  from  a  gallon 
of  water  1 


ZiV  CHEMISTRY.  99 

The  standard  gallon  of  the  United  States  weighs 
8.3389  Ibs.  of  distilled  water. 

Ha  :  H2O  :  :  x  :  8.3389  Ibs. 
2  :     18     :  :  x  :  8.3389  Ibs. 
9  x  =  8.3389  Ibs. 
x  =  .9265  Ib.  (H). 

1  8.  In  decomposing  H3O,  65  parts  by  weight  ofZn  yield 
2  parts  by  weight  0/~H.  How  much  Zn  must  be  employed 
to  obtain  100  Ibs. 


If  we  look  at  the  equation 

H2SOt  +  Zn  =  ZnSO4  4-  H2, 


we  see  that 


H3      signifies     2  parts  by  weight  of  hydrogen, 


H2O  18 

S  "          32 


ZnSO, 


Ot  "  64     '  "   oxygen, 

H2SO4       u          98     "  '         "  sulphuric  acid, 

Zn  "  65     "  l          "   zinc, 


41  water, 
'         "  sulphur, 


zinc  sulphate. 


The  equation,  therefore,  shows  that  98  parts  by  weight 
of  sulphuric  acid  added  to  65  parts  of  zinc  will  form  161 
parts  of  zinc  sulphate,  and,  decomposing  18  parts  of 
water,  liberate  2  parts  of  hydrogen.  For  every  part  of 
H  we  must  have  $£-  parts  of  Zn :  hence,  to  obtain  100 
Ibs.  of  H  we  should  need  100  Ibs.  x  *£•  =  3250  Ibs.  Zn. 
In  a  similar  way  we  can  find  the  amount  of  each  of  the 
other  constituents  needed. 

19.  How  much  KC1O3  would  be  required  to  evolve  suf- 
ficient O  to  burn  the  H  produced  by  the  decomposition  of  2 
Ibs.  ^H2O? 

(See  Key,  page  61,  Question  37.) 


100  ANSWERS   TO  PRACTICAL   QUESTIONS 

20.  How  much  O  would  be  required  to  oxidize  the  metallic 
Cu  which  could  be  reduced  from  its  oxide  by  passing  over  if, 
when  white-hot,  20  gr.  ofH  gas  ? 

(See  Key,  page  60,  Question  34.) 

21.  How  much  O  would  be  required  to  oxidize  the  metallic 
Fe  which  could  be  reduced  in  the  same  manner  by  10  grs. 
of 'H  gas? 

(See  Key,  page  61,  Question  35.) 

22.  Why  are  rose-balloons  so  buoyant  ? 

They  are  filled  with  hydrogen  or  coal-gas,  which  is 
lighter  than  common  air. 

23.  How  much  H  must  be  burned  to  produce  a  ton  of 
water  ? 

Find  how  much  H  is  contained  in  2000  Ibs.  of  water. 

(i).    Ha  :  HaO  :  :  x  :  2000  Ibs. 
2  :     18     :  :  x  :  2000  Ibs. 
18  x  =  4000  Ibs. 

X  =   222|    IbS.   (H). 

zd  Method. — One-ninth  of  any  weight  of  water  is  hydrogen  ;  hence, 
2000  Ibs.  -4-  9  =  222 1  Ibs.  (H). 

94. — i.  Why  does  not  blowing  cold  air  on  a  fire  with  a 
bellows  extinguish  it  ? 

More  heat  is  liberated  by  the  O  which  combines  with 
the  fuel  than  is  withdrawn  from  the  fire  by  the  current  of 
cold  air.  Yet  the  temperature  of  the  fire  must  be  suffi- 
cient to  elevate  that  of  the  O  to  the  point  of  union  with 
C  and  H,  else  the  fire  will  be  extinguished. 

3.    Why  is  fire-damp  more  dangerous  than  choke-damp  ? 
Fire-damp,  or  marsh-gas,  is  inflammable,  while  choke- 
damp,  or  "  carbonic  acid,"  is  not. 


IN  CIIEMISTRY.  10 1 


4.  Represent  the  reaction,  tn\'ifrdkfag  CO  $,'?. bowing  the 

atomic  weights,  as  in  the  £>r£pqrajion  of^Q  on  page  28. 

In  this  experiment  the  acid'  exchanges  its  Tiydrogen  for 
the  calcium,  producing  calcium  chloride  (CaCl2)  on  the 
one  hand,  and  carbonic  acid  (H2CO3)  on  the  other. 
But  the  carbonic  acid  is  so  unstable  that  it  immediately 
becomes  decomposed  into  water,  which  remains  behind, 
and  into  carbonic  anhydride,  which  comes  off  as  a  gas 
with  brisk  effervescence.  The  decomposition  may  be 
represented  as  follows  : 

CaCO3  +  2HC1  =  CaCl2  +  H2O  +  CO2. 

(Calcium  Car-  )   ,  j  (Hydrochlo- )  _  j  (Calcium    I      /Wa^r\  ,  j  (Carbonic 
bonate)          ]  +  \     ric  Acid)     \~\  Chloride)  f+  + 1  Anhydride) 

Ca   C    O3  2(H    CD  Ca     Cla        +   H2  O     +      C     O3 

40  +  12  +  3x16  2(1+35.5)  40  +  2(35.5)  2  +  16  12  +  2x16 


The  CO  liberated  =  Tys  of  the  materials  used ;  the  HaO  =  rV8s,  and  the 
CaCl3  =  HI- 

5.  Should  one  take  a  light  into  a  room  where  the  gas  is 
escaping  ? 

Great  care  should  be  used,  since  coal-gas  is  combus- 
tible, and  when  mixed  with  O  in  the  proper  proportion 
explodes  with  great  violence.  Severe  accidents  frequently 
occur  from  a  neglect  of  this  precaution. 

6.  What  causes  the  difference  between  a  No.  i  and  a  No.  4 
pencil? 

(See  Chemistry,  page  67.) 

7.  Why  does  it  dull  a  knife  to  sharpen  a  pencil1! 

(See  Chemistry,  page  67.) 


102  ANSWERS  TO  PRACTICAL   QUESTIONS 

8.  Why  *V  s/ate  found  fetwcm-  seams  of  coal  ? 

{See-Geotogfr  page  150.) 

The*  'cbai'  represents  a  period  of  vegetation,  and  the 
slate,  one  of  convulsion.  During  the  former,  a  deposit  of 
the  leaves,  branches,  trunks  of  trees,  etc.,  was  made  ; 
during  the  latter,  one  of  gravel,  sand,  etc.,  accumu- 
lated. 

9.  Why  was  the  coal  hidden  in  the  earth  ? 

It  is  natural  to  think  that  one  object  was  to  protect  it 
from  accidental  combustion. 

10.  Where  was  the  C,  now  contained  in  the  coal,  before 
the  Carboniferous  age  ? 

(See  Geology,  pages  150-1.) 

In  the  atmosphere,  which  was  then  so  full  of  CO2  that, 
according  to  certain  authorities,  it  contained  7  to  8  parts 
in  100. 

1 1.  Must  the  air  have  then  contained  more  plant  food  ? 

(See  Chemistry,  page  71,  and  Geology,  page  150.) 

12.  What  is  the  principle  of  the  aquarium  ? 

The  inter-dependence  of  animals  and  plants,  whereby 
each  supplies  the  wants  of  the  other.  The  aquarium  is  a 
microcosm  — a  world  in  miniature. 


*  I  have  read  somewhere  a  beautiful  Persian  fable  in  which  a  nightingale 
and  a  rose  are  represented  as  being  confined  in  a  cage  together,  and  being 
dependent  upon  each  other  for  life.  The  fable  is  truth  symbolized.  The  idea 
has  now  become  more  practical,  but  not  less  beautiful.  In  the  modern 
aquarium ,  or  drawing-room  fish-pond,  we  see  the  world  in  miniature.  It  is  a 
self-regulating,  self-subsisting  establishment,  and  is  constructed  on  the  most 
perfect  principles  of  chemical  economy. 

"  Before  this  truth  of  compensation  between  animals  and  plants  was  dis- 
covered, many  attempts  were  made  to  keep  fish  in  small  glass  globes.  As 


IN  CHEMISTRY.  1 03 

13.  What  test  should  be  employed  before  going  down  in  an 
old  well  or  cellar  ? 

A  lighted  candle  should  be  lowered.  If  that  is  dimmed 
or  extinguished  it  is  not  safe  for  one  to  descend. 

14.  What  causes  the  sparkle  of  wine  and  the  foam  of 
beer  ? 

The  CO 2  formed  in  the  process  of  fermentation. 

15.  What  causes  the  cork  to  fly  out  of  a  catsup  bottle? 
The  CO  2  which  is  produced  when  the  catsup  ferments. 

they  soon  exhausted  the  oxygen,  and  impregnated  the  water  with  carbonic 
acid,  it  was  necessary  to  change  it  daily.  In  this  operation  they  suffered  the 
most  intense  fear.  For  a  few  weeks  they  would  drag  out  a  dubious  exist- 
ence, seemingly  anxious  only  to  find  out  before  they  died  where  they  were  and 
how  they  got  there.  Finally,  but  a  few  years  since,  it  was  discovered  that 
plants  evolve  oxygen  and  consume  carbonic  acid  in  the  water  as  well  as  in 
the  air.  Starting  out  with  this  idea,  about  the  year  1850,  a  Mr.  Warrington, 
an  Englishman,  set  about  breeding  fish  and  mollusks  in  tanks  by  the  aid  of 
marine  plants.  He  succeeded  admirably  for  a  few  days,  but  after  a  time,  a 
change  came  over  his  little  world.  Without  apparent  reason,  the  water 
became  suddenly  impure  and  the  fish  died.  Here  was  a  new  agency  at  work. 
With  the  aid  of  a  microscope,  Mr.  Warrington  explored  his  tank  for  the 
poison  that  was  evidently  latent  there.  He  soon  discovered  that  some  of  his 
plants  had  reached  maturity  and,  in  obedience  to  the  law  of  nature,  had  died. 
The  decaying  matter  was  the  poison  of  which  he  was  in  search.  How  was 
this  to  be  counteracted  ?  In  nature's  tanks — seas,  rivers,  and  ponds — reflected 
Mr.  Warrington,  plants  must  die  and  decay,  yet  this  does  not  destroy  animal 
life.  We  must  see  how  nature  remedies  the  evil.  He  hastened  to  a  pond  in 
the  vicinity  and  examined  its  bottom  with  care.  He  found,  as  he  had  antici- 
pated, an  abundance  of  vegetable  matter  decayed.  He  likewise  found 
swarms  of  water-snails  doing  duty  as  scavengers,  and  devouring  the  putre- 
fying substances  before  they  had  time  to  taint  the  water.  Here  was  the 
secret ;  so  beautiful  a  contrivance  that  it  is  said  Mr.  Warrington,  with  the 
emotion  of  a  true  man  of  science,  burst  into  tears  when  it  flashed  upon  him 
like  a  revelation. 

"  He,  however,  quickly  dried  his  eyes,  gathered  a  quantity  of  snails,  and 
threw  a  handful  into  his  little  tank  at  home.  In  a  single  day  the  water  was 
clear  and  pure  again.  The  fish  throve  and  gamboled,  grew  and  multiplied  ; 
the  plants  resumed  their  bright  colors,  and  the  snails  not  only  rollicked  in  an 
abundance  of  decaying  branches,  but  laid  a  profusion  of  eggs,  on  which  the 
fish  dined  sumptuously  every  day." 


104  ANSWERS  TO  PRACTICAL  QUESTIONS 

1 6.  What  philosophical  principle  does  the  solidification  of 
CO  g  illustrate? 

(See  Philosophy^  page  242.) 

That  evaporation  is  a  cooling  process.  A  portion  of 
the  liquid  CO2  turns  to  vapor,  and  thus  abstracts  so  much 
heat  from  the  remainder  as  to  freeze  it. 

1 7.  Why  does  the  division  in  the  chimney  shown  in  Fig.  28 
produce  two  currents  ? 

For  a  few  moments  there  is  an  uncertainty — a  condi- 
tion of  unstable  equilibrium.  The  heated  air  is  endeavor- 
ing to  rise,  and  the  cold  air  trying  to  come  in  to  supply 
its  place.  The  situation  of  the  candle  in  the  jar  deter- 
mines the  length  of  time  before  the  currents  start.  If  the 
candle  be  placed  on  one  side  of  the  jar  they  will  be 
established  almost  instantly. 

1 8.  What  causes  the  unpleasant  odor  of  coal-gas  ?     Is  it 
useful? 

Impurities  which  it  contains.  Olefiant  gas  has  a  faint 
sweetish  odor,  while  carbonic  oxide  and  hydrogen,  when 
pure,  are  inodorous.  The  disagreeable  smell  is  due  in 
part  to  acetylene  (C2H2).  The  unpleasant  odor  warns 
us  of  the  presence  of  coal-gas. 

19.  What  causes  the  sparkling  often  seen  in  a  gas-light? 

Particles  of  lime  taken  up  mechanically  in  the  process 
of  purification. 

20.  Why  does  H  in  burning  give  out  more  heat  than  C  ? 

i  Ib.  of  H  burned  in  O  emits  heat  sufficient  to  melt 
315.2  Ibs.  of  ice;  and  12  Ibs.  of  carbon  converted  into 
CO 2  enough  to  melt  700  Ibs.  of  ice.  (This  subject  is 


IN  CHEMISTRY.  105 

quite  fully  treated  in  Miller's  Chemical  Physics,  page  294, 
et  seq.)  The  cause  is  not  as  yet  fully  determined,  although 
it  is  perhaps  safe  to  say  that  in  ordinary  combustion  the 
heat  depends  on  the  amount  of  O  which  enters  into  com- 
bination with  the  fuel.  "  Thus  hydrogen  in  burning  takes 
up  three  times  as  much  O,as  C  does,  and  hence  gives  off 
three  times  as  much  heat." — YOUMANS. 

2 1.  Why  does  blowing  on  afire  kindle  it,  and  on  a  lighted 
lamp  extinguish  it  ? 

(See  Key,  page  50,  Question  6.) 

22.  Why  can  we  not  ignite  hard  coal  with  a  match  ? 
Because  it  is  a  good  conductor  of  heat. 

23.  What  causes  the  dripping  of  a  stove-pipe  ? 

The  condensation  of  the  water  formed  in  the  combus- 
tion of  the  fuel. 

24.  Why  will  an  excess  of  coal  put  out  afire  ? 

Because  it  will  absorb  the  heat,  and  thus  reduce  the 
temperature  of  the  fire  below  the  combining  point  of  C 
andO. 

25.  Why  do  not  stones  burn  as  well  as  wood? 
Because  they  are  already  burned,  i.  e.,  combined  with  O. 

26.  Why  does  not  hemlock  make  good  coals  ? 

Because  (i)  of  its  lack  of  C,  and  (2)  its  porous  struc- 
ture. 

27.  What  adaptation  of  chemical  affinities  is  shown  in  a 
light  ? 

If  O  had  the  same  affinity  for  C  that  it  has  for  H,  they 
would  be  consumed  at  once,  with  little  light.  The  fact 


106  ANSWERS  TO  PRACTICAL   QUESTION'S 

that  the  H  burns  first,  and  thus  heats  up  to  the  lumi- 
nous point  the  particles  of  C  as  they  float  outward  to 
the  air,  causes  the  illuminating  power  of  the  hydro- 
carbons. 

28.  Is  there  a  gain  or  a  loss  of  weight  by  combustion  ? 

The  products  of  combustion  weigh  as  much  as  the  fuel 
and  the  O  which  enters  into  combination  with  it. 

29.  Why  does  snuffing  a  candle  brighten  the  flame  ? 

Because  it  removes  the  charred  wick,  which  diminishes 
the  heat  of  the  flame  both  by  conduction  and  radiation. 

30.  Why  is  the  flame  of  a  candle  red  or  yellow ',  and  that 
of  a  kerosene  oil-lamp  white  ? 

(See  Philosophy,  page  225.) 

The  heat  of  a  candle-flame  is  much  less  than  that  of 
kerosene,  and  thus  the  colors  characteristic  of  a  lower 
temperature  are  produced. 

31.  Why  does  blowing  on  a  light  extinguish  it? 

Because  it  lowers  the  temperature  of  the  flame  below 
the  point  of  union  between  O  and  C. 

32.  Why  will  water  put  out  afire? 

(See  Chemistry,  page  93.) 

Partly  by  absorbing  the  heat  of  the  fire,  and  partly  by 
shutting  out  the  O. 

33.  What  should  we  do  if  a  person's  clothes  take  fire  t 

The  best  course  is  to  wrap  the  person  in  a  blanket, 
carpet,  coat,  or  even  in  his  own  garments.  This  smothers 
the  fire  by  shutting  out  the  O. 


IN  CHEMISTRY.  107 

34.  Ought  we  to  leave  open  the  doors  or  windows  of  a 
burning  house  ? 

(See  Chemistry,  page  93.) 

No.  Open  doors  or  windows  will  make  draughts  of  air 
to  feed  the  flame. 

35.  Why  does  a  street  gas-light  burn  blue  on  a  windy 
night  ?     Is  the  light  then  as  intense  ?     The  heat  ? 

O  is  mingled  with  the  flame  in  sufficient  quantities  to 
burn  the  H  and  C  simultaneously.  Thereby  the  heat  is 
increased,  but  the  light  diminished.  The  principle  is  that 
of  Bunsen's  burner. 

36.  Why  does  not  the  lime  burn  in  a  calcium-light? 
Lime  is  a  burned  body;  its  symbol  is  CaO. 

37.  Why  is  a  candle-flame  tapering? 

(See  Chemistry,  page  88.) 

The  currents  of  air  rushing  toward  the  flame  from  all 
sides  give  it  the  conical  form. 

38.  Why  does  a  draught  of  air  cause  a  lamp  to  smoke  ? 

It  lowers  the  heat  of  the  flame  below  the  point  of  union 
between  C  and  O,  and  thus  the  C  is  precipitated. 

39.  What  makes  the  coal  at  the  end  of  a  candle-wick  ? 

The  wick  at  the  edge  of  the  flame  comes  in  contact 
with  the  O  of  the  air,  and  therefore  burns. 

40.  Which  is  the  hottest  part  of  a  flame? 

Toward  the  point  of  the  cone,  where  the  gaseous  en- 
velopes meet  and  make  a  solid  flame. 


IO  ANSWERS  TO  PRACTICAL  QUESTIONS 

41.  Why  does  not  a  candle-wick  burnt 
There  is  no  O  at  the  centre  of  the  flame. 

42.  How  does  a  chimney  enable  us  to  burn  highly  car- 
boniferous substances  like  oil  without  smoke  ? 

(See  Chemistry,  page  88.) 

It  keeps  out  the  cold  air,  and  elevates  the  temperature 
of  the  O,  which  supplies  the  flame.  Thus  more  C  can  be 
consumed. 

43.  How  much  CO  2  in  200  Ibs.  of  chalk? 

CO,  :  CaCO3  :  :  x  :  200  Ibs. 
44  :      100       :  :  x  :  200  Ibs. 

100  x  —  8800  Ibs. 

x  =  88  Ibs.  (CO2). 

44.  What  weight  of  CO  %  in  a  ton  of  marble  1 

CO2  :  CaCO3  :  :  x  :  2000  Ibs. 
44  :      100       :  :  x  :  2000  Ibs. 

zoo  x  —  88,000  Ibs. 
x  =  880  Ibs.  (CO3). 

45.  What  is  the  difference  between  marble  and  chalk  ? 

Marble  is  a  compact,  crystallized  carbonate  of  lime, 
while  chalk  is  a  porous  kind  of  limestone. 

46.  Why  does  not  a  cold  saucer  held  over  an  alcohol  flame 
blacken,  as  it  does  over  a  candle  or  gas-light  ? 

There  is  less  C  in  alcohol  than  in  tallow  or  in  coal-gas. 

47.  Could  a  light  be  frozen  out,   i.  e.,  extinguished,  by 
merely  lowering  the  temperature  ? 

It  is  said  to  have  been  done  in  Arctic  regions. 


IN  CHEMISTRY.  IO9 

48.  How  much  CO2  is  formed  in  the  combustion  of  one 
ton  of  Cl 

C  :  COa  :  :  2000  Ibs.  :  x. 

12  :    44     :  :  2000  Ibs.  :  x. 

12  x  =  88,000  Ibs. 

*  =  7333-33+  Ibs.  (CO2). 

49.  What  weight  of  C  is  there  in  a  ton  of  CO8  ? 

C  :  COa  :  :  x  :  2000  Ibs. 

12  :    44     :  :  x  :  2000  Ibs. 

44  x  —  24,000  Ibs. 

^  =  545-45  +  Ibs.  (C). 

50.  How  much  O  is  consumed  in  burning  a  ton  ofCJ 

In  any  quantity  of  CO2,  -fj-  of  the  compound  is  O,  and 
^  C.  If  -j^-  =  2000  Ibs.  (CO2),  then  -^  =  f  of  2000  Ibs. 
=  5333-33  +  Ibs.  (O). 

51.  What  weight  of  sodium  carbonate  (Na2CO3,  ioH2O, 
"  carbonate  of  soda  ")  would  be  required  to  evolve  12   Ibs. 
<?/C02? 

COa  :  NaaCO3,  ioHaO  :  :  12  Ibs.  :  x. 
44  :  286  :  :  12  Ibs.  :  x. 

44  x  =  2432  Ibs. 

x  =  50.72  Ibs.  (NaaCO3,ioHaO). 

52.  How  much  CO 2  will  be  formed  in  the  combustion  of 

CO  :  COa  :  :  30  grs.  :  x, 

28  :    44     :  :  30  grs.  :  x. 

28  x  =  1320  grs. 

x  =  47.14  grs.  (COa). 

5  3 .  What  weight  of  hydrogen  sodium  carbonate  ( H  NaCO  3 , 
"  bi-carbonate  of  soda  ")  would  be  required  to  evolve  12  Ibs. 

C0a  :  HNaC03  :  :  12  Ibs.  :  x. 
44  :         84         :  .-  12  Ibs.  :  x. 
44  x  =  1008  Ibs. 

x  =  22.9  Ibs.  (HNaCO,). 


HO  ANSWERS  TO  PRACTICAL  QUESTIONS 

54.    Write  in  double  columns  the  different  properties  of 
carbonic  anhydride  and  carbonic  oxide. 


1.  COS. 

2.  Atomic  weight — 44. 

3.  Specific  gravity— 1.529. 

4.  Will  not  burn. 

5.  A  negative  poison. 

6.  Liquefies  at  32°,  and  a  pressure 

of  38.5  atmospheres. 

7.  Freely  soluble  in  H2O. 

8.  Forms  salts. 

&c.,  &c. 


1.  CO. 

2.  Atomic  weight — 28. 

3.  Specific  gravity — .967. 

4.  Burns  with  a  blue  flame. 

5.  A  direct  poison. 

6.  Has  never  been  liquefied. 

7.  Sparingly  soluble  in  water. 

&c.,  &c. 


1 1 8. — i.  If  chlorine  water  stands  in  the  sunlight  for  a 
time,  it  will  only  redden  a  litmus-solution.  Why  does  it  not 
bleach  it? 

Hydrochloric  acid  is  formed,  which  reddens  the  lit- 
mus. 

2.  Why  do  tinsmiths  moisten  with  HC1,  or  sal-ammoniac, 
the  surface  of  metals  to  be  soldered  ? 

It  dissolves  the  coating  of  oxide  and  leaves  the  surface 
of  the  metal  free  for  the  action  of  the  solder. 

3.  How  much  HC1  can  be  made  from  25  Ibs.  of  common 
salt  ? 

Find  (i)  how  much  Cl  there  is  in  25  Ibs.  of  NaCl,  and 
(2)  how  much  HC1  that  amount  of  Cl  would  make. 

(i).    Cl  :  NaCl  :  :  x  :  25  Ibs. 
35-5  :    58.5     ::  x  :  25  Ibs. 
58.5  »  =  887.5  Ibs. 

x  =  15.17094  Ibs.  (Cl). 

(2).  Cl  :  HC1  :  :  15.17094  Ibs.  :  x. 
35-5  :  36-5  :  :  i5-i7°94  Ibs.  :  x. 
35-5  x  -  553-73931  Ibs. 

x  -  15.5980056-1-  Ibs.  (HC1). 


IN  CHEMISTRY.  Ill 

4.  What  weight  of  NaCl  would  be  required  to  form  25 
Ibs.  of  muriatic  acid  ? 

(See  Key^  page  58,  Question  20.) 

5.  HC1  of  a  specific  gravity  of  1.2  contains  about  ^  per 
cent,   of  the  gas.     This   is   very   strong  commercial  acid. 

What  weight  could  be  formed  by  the  HC1  acid  gas  produced 
in  the  reaction  named  in  the  preceding  problem  ? 

(See  Key,  page  58,  Question  21.) 

6.  What  is  the  difference  between  sublimation  and  distilla- 
tion ? 

A  body  is  said  to  sublime  when  it  rises  as  vapor  and 
condenses  in  the  solid  form ;  when  it  condenses  as  a  liquid 
it  is  said  to  distil. 

7.  Why  do  eggs  discolor  silver  spoons  ? 

The  sulphur  of  the  egg  combines  with  the  Ag,  forming 
silver  sulphide — the  black  sulphuret  of  silver. 

8.  Explain  the  principle  of  hair-dyes. 

The  two  principal  chemicals  used  for  dyeing  the  hair  are 
lead  and  silver  nitrate.  The  S  in  the  hair  combining  with 
the  Ag  makes  silver  sulphide,  or  with  the  Pb,  lead  sul- 
phide, either  of  which  stains  the  hair :  the  former  colors 
the  skin  as  well  as  the  hair,  while  the  latter  is  absorbed 
through  the  skin,  causing  colics  and  other  diseases  such 
as  are  common  among  painters.  The  "golden  yellow 
color"  lately  in  fashion  is  produced  by  a  solution  of  ar- 
senic with  the  hydrosulphate  of  ammonia.  In  order  to 
dye  the  lighter  tints,  it  is  necessary  to  bleach  the  hair 
with  an  alkaline  solution.  See  Fireside  Science,  page  77. 


112  ANSWERS  TO  PRACTICAL  QUESTIONS 

9.  Why  is  new  flannel  apt  to  turn  yellow  when  washed  ? 

New  flannels,  washed  in  strong  soap,  turn  yellow,  be- 
cause the  alkali  of  the  soap  unites  with  the  SO2  used  in 
bleaching  the  cloth,  and  thus  sets  free  the  original  color. 

10.  Is  it  safe  to  mix  oil  of  vitriol  and  water  in  a  glass 
bottle  ? 

The  heat  produced  by  the  combination  of  the  two  will 
be  liable  to  break  the  glass. 

11.  What  is  the  color  of  a  sulphuric  acid  stain  on  cloth  ? 
How  would  you  remove  it? 

It  is  generally  red,  especially  on  black  cloth.  The 
color  may  be  restored  by  a  few  drops  of  a  solution  of 
common  "soda." 

12.  What  causes  the  milky  look  when  oil  of  vitriol  and 
water  are  mixed  ? 

Pb  from  the  stills  in  which  the  acid  is  condensed,  and 
which  is  soluble  in  strong  H2SO4,  is  precipitated  when 
the  acid  is  diluted  with  HSO. 

13.  What  is  the  relation  between  animals  and  plants  ? 
Which  perform  the  office  of  reduction,  and  which  that  of 

oxidation  ? 

(See  AVy,  page  52,  Question  19.) 

14.  How  many  pounds  of  S  are  contained  in  100  Ibs.  of 
H2SO4? 

S  :  H2SO4  :  :  x  :  100  Ibs. 
32  :       98       :  :  x  :  100  Ibs. 
98  x  =  3200  Ibs. 
x  =  32-Jf  Ibs.  (S). 


IN  CHEMISTRY.  113 

15.  How  much  O  and  H2O  are  needed  to  change  a  ton 
of  SO2  /*H8SO4? 

One  ton  of  SO2  will  make  i£f  tons  of  H2SO4  :  of 
which  -fa  is  H,  Jf  is  S,  and  £f  is  O.  i  of  this  O,  or  ^ 
comes  from  the  air,  and  i  =  ^  ^rom  ^e  water-  (See  pro- 
cess of  manufacture,  Chemistry,  p.  116.)  Hence  -fa  (O) 
and  j^.  (H)  =  -£§  of  the  acid  was  furnished  by  the  water  — 
-fs  of  i-y-  tons  =  -^g-  ton  (H2O).  The  process  of  reason- 
ing may  be  seen  more  clearly,  perhaps,  by  preparing  the 
formulae  as  in  Question  18,  page  99,  of  this  Key. 

1  6.  How  much  O  in  a  Ib.  <?/~H2SO4  ? 

f  f-  of  any  quantity  of  sulphuric  acid  are  O  ;  -fa  is 
H  ;  and  £f  are  S.  Hence  in  i  Ib.  of  H2SO2  there  are 


17.  State  the  analogy  between  the  compounds  qfO  and  S. 


o 

HaO 

H2O2  (hydrogen  dioxide) 

C03 


S 

H2S 

H2Sa 

CS2 


The  corresponding  compounds  possess  not  only  an  an- 
alogous composition,  but  also  similar  chemical  proper- 
ties. 

146. — i.  In  the  experiment  with  Na2SO4,  on  page  133, 
an  accurate  thermometer  will  show  that  in  making  the  solu- 
tion^ the  temperature  of  the  liquid  will  fall,  and  in  its  solidi- 
fication,  will  rise.  Explain. 

(See  Philosophy,  page  233.) 

The  solid  salt  passing  into  a  liquid  takes  up  heat, 
and,  in  returning  from  a  liquid  to  a  solid  again,  gives 
up  heat.  The  latter  is  illustrated  in  next  question. 


H4  ANSWERS  TO  PRACTICAL   QUESTIONS 

2.  If,  in  making  a  solution  of  Na2SO4,  we  use  the  salt 
which  has  effloresced,  and  so  become  anhydrous,  the  tempera- 
ture will  rise  instead  of  falling  as  before.     Explain. 

This  is  because  a  solid  hydrate  is  formed  before  the 
salt  dissolves  in  the  H2O.  The  same  holds  true  of  other 
anhydrous  bodies,  as  the  chlorides  of  Zn,  Fe,  and  Cu. 

3.  Why  is  KNO3  used  instead  of  NaNO3  for  making 
gunpowder  ? 

Sodium  nitrate  is  imported  from  Chili  in  large  quanti- 
ties, and  attempts  have  been  made  to  use  it  for  making 
gunpowder,*'  but  its  tendency  to  attract  moisture  has 
frustrated  the  plan.  It  is  now  extensively  used  as  a  fer- 
tilizer, and  is  said  to  be  the  cheapest  form  in  which  N 
can  be  furnished  the  soil. 

4.  Why  is  a  potassium  salt  preferable  to  a  sodium  one  in 
glass-making  ? 

Sodium  salts  give  a  greenish  tint  to  the  glass. 

*  Gunpowder  is  an  intimate  mechanical  mixture  of  about  i  part  nitre,  i  part 
sulphur,  and  3  parts  charcoal.  These  proportions,  however,  vary  somewhat 
in  different  countries,  as  well  as  in  different  sorts  of  powder.  More  charcoal 
adds  to  its  power,  but  also  causes  it  to  attract  moisture  from  the  air,  which  of 
course  injures  its  quality.  For  blasting  rocks,  where  a  sustained  force,  rather 
than  an  instantaneous  one,  is  required,  the  powder  contains  more  sulphur, 
and  is  even  then  often  mixed  with  sawdust  to  retard  the  explosion.  The 
nitre,  sulphur,  and  charcoal,  having  been  ground  and  sifted  separately,  are 
thoroughly  mixed  and  then  made  into  a  thick  paste  with  water.  This  is 
ground  for  some  hours  under  edge-stones,  after  which  it  is  subjected  to  im- 
mense pressure  between  gun-metal  plates,  forming  what  is  known  as  press- 
cake.  These  cakes  are  then  submitted  to  the  action  of  toothed  rollers,  where- 
by the  granulation  of  the  powder  is  effected.  The  grains  thus  formed  are 
sorted  into  different  sizes  by  means  of  a  series  of  sieves,  and  thoroughly  dried 
at  a  steam  heat.  The  last  operation,  that  of  polishing,  is  accomplished  in  re- 
volving barrels,  after  which  the  powder  is  ready  for  market.  The  heavier 
the  powder,  the  greater  is  its  explosive  power.  Good  powder  should  resist 
pressure  between  the  fingers,  giving  no  dust  when  rubbed,  and  have  a 
slightly  glossy  aspect.— YOUMANS. 


IN  CHEMISTRY.  11$ 

5.  What  is  the  glassy  slag  so  plentiful  about  a  furnace  ?  * 

A  silicate  of  lime  or  some  other  base  contained  in  the 
ore. 

Ordinary  Slag  from  Blast  Furnace  (Bloxani). 

Silica 43.07 

Alumina 14-85 

Lime 28.92 

Magnesia 5.87 

Oxide  of  iron  2.53 

Oxide  of  manganese -. 1-37 

Potash 1.84 

Sulphide  of  calcium 1.90 

Phosphoric  acid trace 

100.35 

6.  State  the  formula  of  nitre,  saleratus,  carbonate  and 
bicarbonate  of  soda,  plaster,  pearlash,  saltpetre,  plaster  of 
Paris,  gypsum,  carbonate  and  bicarbonate  of  potash,  sal-soda* 
and  soda. 

Nitre,  saltpetre KNO3. 

Saleratus,  pearlash HKCOS. 

Carbonate  of  soda,  sal-soda. NaaCO3. 

Bicarbonate  of  soda,  "soda".... HNaCO3. 

Plaster,  gypsum CaSO4,2HsO. 

Plaster  of  Paris CaSO«. 

7.  Explain  how  ammonium  carbonate  is  formed  in  the 
process  of  making  coal-gas. 

Nitrogen  exists  in  small  quantities  in  coal,  and  when 
that  is  distilled  at  a  high  temperature,  the  elements  in 
their  nascent  state  combine  to  form  this  compound. 

*  The  slag  is  commonly  employed  for  road-making  in  the  neighborhood  of 
the  iron-works.  Some  attempts  have  been  made  to  turn  the  slag  to  account 
by  employing  it  as  a  manure  for  soils  deficient  in  potash,  of  which  it  will  be 
seen  that  the  above  slag  contains  nearly  s\jth  of  its  weight,  in  a  form  which 
would  be  easily  rendered  available  for  plants  by  the  combined  action  of  air 
and  moisture.  When  the  slag  is  run  into  water,  or  blown  into  a  frothy  con- 
dition by  the  blast,  it  resembles  pumice-stone,  and  is  easily  ground  to  a  pow- 
der fit  for  applying  to  the  soil. 


Il  ANSWERS  TO  PRACTICAL  QUESTIONS 

8.  Upon  what  fact  depends  the  formation  of  stalactites  ? 

Water  containing  carbonic  acid  in  solution  will  dissolve 
carbonate  of  lime  freely,  but  when,  on  exposure  to  the 
air,  the  gas  escapes,  the  carbonate  is  deposited. 

9.  Why  is  HF  kept  in  gutta-percha  bottles  ? 

Because  it  will  dissolve  silica,  and  so  destroy  a  glass 
bottle. 

10.  Explain  the  use  of  borax  in  softening  hard  water? 

It  softens  hard  water  by  uniting  with  the  soluble  salts 
of  lime  or  magnesia,  and  making  insoluble  ones  which 
settle  and  form  a  thin  sediment  in  the  bottom  of  pitchers 
in  which  it  is  placed. 

1 1 .  How  are  petrifactions  formed  ? 

Certain  springs  contain  large  quantities  of  some  alka- 
line carbonate ;  their  waters,  therefore,  dissolve  silica 
abundantly.  If  we  place  a  bit  of  wood  in  them,  as  fast 
as  it  decays,  particles  of  silica  will  take  its  place — atom 
by  atom — and  thus  petrify  the  wood.  The  wood  has 
not  been  changed  to  stone,  but  has  been  replaced  by  stone. 

12.  In  what  part  of  the  body,  and  in  what  forms ,  is 
phosphorus  found  ? 

As  a  phosphate  if  is  the  principal  earthy  constituent  of 
the  bones.  It  is  also  a  never-failing  ingredient  of  the 
brain  and  nervous  system.  The  susceptibility  of  phos- 
phorus to  oxidation  especially  adapts  it  to  the  rapid 
changes  incident  to  the  structure  and  offices  of  the 
brain.* 

*  Phosphorus  is  an  element  which  can  imperceptibly  and  quickly  pass  from 
a  condition  of  great  chemical  activity  to  one  of  equal  chemical  inertness.    In 


IN  CHEMISTRY.  1 17 

13.    Why  are  matches  poisonous  ?       What  is  the  anti- 
dote? 

(See  Physiology,  page  209.) 

Because  of  the  phosphorus  in  the  match. 


virtue  of  this  character,  it  u  may  follow  the  blood  in  its  changes,  may  oxidize 
in  the  one  great  set  of  capillaries,  and  be  indifferent  to  oxygen  in  the  other  ; 
may  occur  in  the  brain,  in  the  vitreous  form,  changing  as  quickly  as  the 
intellect  or  imagination  demands,  and  literally  flaming  that  thoughts  may 
breathe  and  words  may  burn  ;  and  may  be  present  in  the  bones  in  its  amor- 
phous form,  content  like  an  impassive  caryatid,  to  sustain  upon  its  unwearied 
shoulders  the  mere  dead  weight  of  stones  of  flesh.  And  what  is  here  said  of 
the  brain  as  contrasted  with  the  bones,  will  apply  with  equal  or  similar  force 
to  many  other  organs  of  the  body.  All  throughout  the  living  system,  we 
may  believe  that  phosphorus  is  found  at  the  centres  of  vital  action  in  the 
active  condition,  and  at  its  outlying  points  in  the  passive  condition.  In  the 
one  case  it  is  like  the  soldier  with  his  loaded  musket  pressed  to  his  shoulder 
and  his  finger  on  the  trigger,  almost  anticipating  the  command  to  fire  ;  in  the 
other  it  is  like  the  same  soldier  with  his  unloaded  weapon  at  his  side  standing 
at  ease." 

"  Further,  phosphorus  forms  with  oxygen  a  powerful  acid,  capable  even  of 
abstracting  water  from  sulphuric  acid,  and  yet  perfectly  unirritating  to  the 
organic  textures.  Taking  up  varying  quantities  of  water,  phosphoric  acid 
assumes  no  fewer  than  three  distinct  forms,  which  will  unite  with  one,  two, 
or  three  atoms  of  alkali  respectively,  giving  an  acid,  neutral  or  alkaline  reac- 
tion. Thus  it  is  available  for  the  most  varied  uses  in  the  body.  A  child  is 
beginning  to  walk,  and  the  bones  of  its  limbs  must  be  strengthened  and 
hardened  ;  phosphoric  acid,  accordingly,  carries  with  it  three  units  of  lime  to 
them,  and  renders  them  solid  and  firm.  But  the  bones  of  its  skull  must 
remain  comparatively  soft  and  yielding,  for  it  has  many  a  fall,  and  the  more 
elastic  these  bones  are,  the  less  will  it  suffer  when  its  head  strikes  a  hard 
object ;  so  that  in  them  we  may  suppose  the  phosphoric  acid  to  retain  but  two 
units  of  lime,  and  to  form  a  softer,  less  consistent  solid.  And  the  cartilages 
of  the  ribs  must  be  still  more  supple  and  elastic,  so  that  in  them  the  phos- 
phoric acid  may  be  supposed  to  be  combined  with  but  one  unit  of  base.  On 
the  other  hand,  its  teeth  must  be  harder  than  its  hardest  bones,  and  a  new 
demand  is  made  on  the  lime-phosphates  to  associate  themselves  with  other 
lime-salts  (especially  fluoride  of  calcium),  to  form  the  cutting  edges  and 
grinding  faces  of  the  incisors  and  molars.  All  the  while,  also,  the  blood  must 
be  kept  alkaline,  that  oxidation  of  the  tissues  may  be  promoted,  and  albumen 
retained  in  solution  ;  and  yet  it  must  not  be  too  alkaline,  or  tissues  and  albu- 
men will  both  be  destroyed,  and  the  carbonic  acid  developed  at  the  systemic 
capillaries  will  not  be  exchanged  for  oxygen  when  the  blood  is  exposed  to 
that  gas  at  the  lungs.  So  phosphoric  acid  provides  a  salt  containing  two 


Il8  ANSWERS  TO  PRACTICAL   QUESTIONS 

14.  Will  the  burning  phosphorus  ignite  the  wood  of  the 
match  ? 

It  does  not  give  off  enough  heat  in  its  oxidation  to 
raise  the  temperature  of  the  wood  to  the  igniting  point. 
Many,  however,  claim  the  true  reason  to  be  that,  in  burn- 
ing, it  produces  an  ash  (P2O5)  which  covers  the  wood  as 
with  a  varnish  and  so  protects  it  from  oxidation. 

15.  What  philosophical  principle  is    illustrated  in  the 
ignition  of  a  match  by  friction  ? 

(See  Philosophy,  page  230.) 

The  conversion  of  motion  into  heat. 

1 6.  How  much   H2O  would  be  required  to  dissolve  a 
pound  of  "KNO3  ? 

3 £  Ibs.  of  cold  water  and  \  Ib.  of  hot  water. 

17.  What  causes  the  bad  odor  after  the  discharge  of  a 
gun? 

The  potassium  sulphide  gradually  gives  up  its  S  to 
form  HgS. 

1 8.  Write  in  parallel  columns  the  properties  of  common 
and  of  red  phosphorus. 


units  of  soda  and  one  of  water,  which  is  sufficiently  alkaline  to  promote 
oxidation,  dissolve  albumen,  and  absorb  carbonic  acid,  and  yet  holds  the  lat- 
ter so  loosely,  that  it  instantly  exchanges  it  for  oxygen  when  it  encounters 
that  gas  in  the  pulmonary  capillaries.  Again,  the  flesh  juice  must  be  kept 
acid  (perhaps  in  opposition  to  the  alkaline  blood,  as  affecting  the  transmission 
of  the  electric  currents  which  traverse  the  tissues),  and  phosphoric  acid  pro- 
vides a  salt,  containing  two  units  of  water  and  one  of  potash,  which  secures 
the  requisite  acidity."— DR.  G.  WILSON,  Edinburgh  Essays,  1856. 


IN  CHEMISTRY. 


Common  phosphorus. 


i.  Specific  gravity— 1.83. 
a.  Burns  at  iu°. 

3.  Odor  of  garlic. 

4.  Soluble  in  CS2. 

5.  Colorless,,  or  straw-yellow. 

6.  A  deadly  poison. 


Amorphous  phosphorus. 


1.  Specific  gravity— 2.14. 

2.  Burns  at  500'. 

3.  Odorless. 

4.  Insoluble  in  CSa. 

5.  Red  often  rivalling  vermilion. 

6.  Harmless. 


19.  What  causes  the  difference  between  fine  and  coarse 
salt? 

(See  Chemistry,  page  132.) 

The  rapidity  of  evaporation  in  the  process  of  manu- 
facture. 

20.  Why  do  the  figures  in  a  glass  paper-weight  look  larger 
when  seen  from  the  top  than  from  the  bottom  ? 

The  form  of  the  glass  acts  like  a  convex  lens  to  mag- 
nify the  apparent  size  of  the  figures. 

21.  What  is  the  difference  between  water-slacked  and  air- 
slacked  lime  ? 

The  former  is  simply  calcium  hydrate,  CaO,  H2O,  while 
the  latter  is  hydratecl  calcium  carbonate,  CaO,  CO2, 
H80  (?). 

22.  Why  do  oyster-shells  on  the  grate  of  a  coal- stove  pre- 
vent the  formation  of  clinkets  ? 

The  lime  of  the  shells  acts  as  a  flux  with  the  iron  in 
the  coal,  thus  dissolving  the  clinkers,  if  any  form. 

23.  How  is  lime-water  madej/om  oyster-shells  ? 

The  shells  are  burned,  driving  off  the  CO3  combined 
with  the  CaO  in  the  CaCO3,  and  the  lime  thus  formed  is 
slightly  soluble  in  water. 


120  ANSWERS   TO  PRACTICAL   QUESTIONS 

24.  Why  do  newly  plastered  walls  remain  damp  so  long? 

The  plaster  or  mortar  in  drying  gives  off  the  water  the 
lime  took  up  in  slacking. 

25.  Will  lime  lose  its  beneficial  effect  upon  a  soil  after 
frequent  applications  ? 

(See  Key,  page  51,  Question  12.) 

26.  What  causes  plaster  of  Paris  to  harden  again  after 
being  moistened  ? 

(See  Chemistry ,  page  139.) 

It  recombines  with  the  water  which  was  driven  off  in 
the  process  of  its  manufacture. 

27.  What  is  the  difference  between  sulphate  and  sulphite 
of  lime'} 

The  former  is  a  compound  of  sulphuric  acid ;   the  lat- 
ter of  sulphurous  acid. 

28.  What  two  classes  of  rays  are  contained  in  the  mag- 
nesium light? 

(See  Philosophy,  page  206.) 

The  actinic  or  chemical,  and  the  colorific  or  luminous 
rays. 

29.  What  rare  metals  would  become  useful  in  the  arts,  if 
the  process  of  manufacture  were  cheapened  ? 

Magnesium,  aluminum,  sodium,  etc. 

30.  What  is  the  rational  formula  for  calcium  carbonate  ? 
Calcium  sulphite  ?     Calcium  sulphate  ? 

1.  CaCO3  =  CaO,CO2. 

2.  CaSO3  =  CaO,SO2. 

3.  CaSO4   =  CaO,SO3. 


IN   CHEMISTRY.  121 

31.  Why  is  lime  placed  in  the  bottom  of  a  leach-tub  I 

The  potash  of  the  ashes  is  generally  in  the  form  of  a 
carbonate,  the  acid  neutralizing  in  part  the  strength  of  the 
alkali.  The  lime  combines  with  the  CO2. 

32.  Is  saleratus  a  salt  of  K  or  of  Na  ? 

It  should  be  a  carbonate  of  K,  but,  on  account  of  its 
cheapness,  the  corresponding  salt  of  Na  is  often  sold  in- 
stead. 

33.  Why  will  Na  burst  into  a  blaze  when  thrown  on  hot 
water  ? 

The  heat  of  the  water  raises  the  hydrogen  to  the  ignit- 
ing point.  This  catches  fire,  and  the  volatilized  Na  colors 
the  flame. 

34.  Why  are  certain  kinds  of  brick  white  ? 

They  contain  no  iron,  this  being  the  substance  which 
by  its  oxidation  gives  the  color  to  common  brick. 

35.  Illustrate  the  force  of  chemical  affinity. 

The  tremendous  force  of  chemical  affinity  forms  with  O 
half  the  crust  of  the  earth.  Yet  when  the  chemist  sets  the 
O  free  from  its  prison-house,  it  comes  before  him  a  transpa- 
rent, invisible  gas,  and  he  cannot  condense  it  to  a  solid  or 
liquid  state  by  any  mechanical  process. 

176. — i.  Pb  is  softer  than  Fe  ;  why  is  it  not  more  mal- 
leable? 

The  facility  with  which  a  mass  of  metal  can  be  ham- 
mered or  rolled  into  a  thin  sheet  without  being  torn,  must 
depend  partly  upon  its  softness,  and  partly  upon  its  tena- 
city. If  it  depended  upon  softness  alone,  lead  should  be 


122  ANSWEES  TO  PRACTICAL   QUESTIONS 

the  most  malleable  of  ordinary  metals  ;  but,  although  it  is 
easy  to  hammer  a  mass  of  lead  into  a  flat  plate,  or  to 
squeeze  it  between  rollers,  any  attempt  to  reduce  it  to  an 
extremely  thin  sheet  fails  from  its  want  of  tenacity,  which 
causes  it  to  be  worn  into  holes  by  percussion  or  friction. 
On  the  other  hand,  if  malleability  were  entirely  regulated 
by  tenacity,  iron  would  occupy  the  first  place,  whereas,  on 
account  of  its  hardness,  it  is  the  least  malleable  of  metals 
in  ordinary  use ;  whilst  gold,  occupying  an  intermediate 
position  with  respect  to  tenacity,  is  the  most  malleable, 
which  appears  surprising  to  those  who  are  only  acquainted 
with  gold  in  its  ordinary  forms  of  coin  and  ornament,  in 
which  it  is  hardened  and  rendered  much  less  malleable 
by  the  presence  of  copper  and  silver. 

I.— Relative  Malleability  of  the  Metals. 

1.  Gold.  4.  Tin.  7.  Zinc. 

2.  Silver.  5.  Platinum.  8.  Iron. 

3.  Copper.  6.  Lead. 

II.— Relative  Tenacity  of  the  Metals. 


Lead        

i 

Silver  

12* 

Tin...           

i| 

Platinum  

Zinc        

2 

Copper   .  . 

....  18 

n> 

Iron 

27i 

Gold... 

..     12 

Steel  .  .  . 

..    42 

III.— Relative  Ductility  of  the  Metals. 

1.  Gold.  5.  Copper.  8.  Zinc. 

2.  Silver.  6.  Palladium.  9.  Tin. 

3.  Platinum.  7.  Aluminum.  10.  Lead. 

4.  Iron.  — BLOXAM. 

2.    What  is  the  cause  of  the  changing  color  often  seen  in 
the  scum  on  standing  water  ? 

(See  "  Interference  of  Light,"  Philosophy,  page  209.) 

The  thin  pellicles  of  iron-rust  on  standing  H2O  pro- 


IN  CHEMISTRY.  123 

duce  a  beautiful  iridescent  appearance,  the  color  changing 
with  the  thickness  of  the  oxide.  A  soap-bubble  exhibits 
in  the  same  way  a  play  of  variegated  colors  according  to 
the  thickness  of  the  film  in  different  parts. 

3.  How  can  the  spectra  of  the  metals  be  obtained? 

(See  Astronomy,  page  285.) 

By  looking  through  a  prism  at  a  flame  containing  min- 
ute portions  of  the  volatilized  metal. 

4.  Ought  cannon,  car-axles,  etc.,  to  be  used  until  they  break 
or  wear  out  ? 

Cannon  are  condemned  and  recast  after  being  fired  a 
certain  number  of  times,  even  though  they  show  no  flaw, 
as  the  jarring  to  which  they  are  exposed  causes  the  iron 
to  take  on  a  crystalline  form  and  become  less  fibrous  and 
tough.  A  cast-iron  gun  of  lo-inch  bore  or  less,  ought  to 
stand  1000  rounds ;  larger  calibres,  a  smaller  number. 

5.  Why  is  "  chilled  iron"  used  for  safes  ? 

The  iron  being  cooled  so  instantaneously,  the  crystals 
are  exceedingly  small,  and  the  metal  is  correspondingly 
harder  than  when  cast  in  the  ordinary  way. 

6.  Does  a  blacksmith  plunge  his  work  into  water  merely 
to  cool  it  ? 

The  metal  is  harder  when  cooled  quickly  and  therefore 
resists  wear  longer. 

7.  What  causes  the  white  coating  made  when  we  spill 
water  on  zinc  ? 

The  oxide  of  zinc  which  is  formed  on  the  surface  of  the 
metal  through  the  favoring  influence  of  the  water. 


124  ANSWERS   TO  PRACTICAL   QUESTIONS 

8.  Is  it  well  to  scald  pickles ,  make  sweetmeats,  or  fry  cakes 
in  a  brass  kettle  ? 

(See  Chemistry,  page  159.) 

9.  What  danger  is  there  in  the  use  of  lead  pipes  ?     Is  a 
lining  of  Zn  or  Sn  a  protection  ? 

(See  Chemistry,  pages  156  and  160,  and  Fireside  Science,  page  149.) 

Zinc  and  tin  are  corroded  by  oxygen,  though  less  read- 
ily than  Pb,  and,  while  their  salts  are  poisonous,  the  lead 
is  soon  laid  bare,  and  this  also  oxidizes. 

10.  Is  water  which  has  stood  in  a  metal-lined  ice-pitcher 
healthful? 

(See  Chemistry,  page  157.) 

The  dissimilar  metals  fastened  with  solder  which  cor- 
rodes in  the  presence  of  water,  develop  a  galvanic  current 
which  hastens  the  oxidation.  The  salts  thus  formed  are 
very  dangerous. 

11.  If  you  ask  for  " cobalt"  at  a  drug-store,  what  will 
you  get  ?     If  for  "  arsenic  ?  ' ' 

Impure  metallic  arsenic  is  sold  as  "cobalt,"  while 
arsenious  anhydride  is  called  "arsenic." 

12.  What  two  elements  are  fluid  at  ordinary  tempera- 
tures ? 

Bromine  and  mercury. 

13.  Should  we  touch  a  gold  ring  to  mercury  ? 

The  mercury  will  form  with  the  gold  an  amalgam. 


IN  CHEMISTRY.  125 

14.  Why  does  silver  blacken  if  handled? 

The  perspiration  of  the  body  contains  S,  which  combin- 
ing with  the  metal  forms  silver  sulphide — the  black  sul- 
phuret  of  silver. 

15.  Why  does  silver  tarnish  rapidly  where  coal  is  used 
for  fires  ? 

S,  which  is  present  in  coal,  is  set  free  by  combustion 
and  forms  a  silver  sulphide. 

1 6.  Why  is  a  solution  of  a  coin  blue? 

From  the  Cu  which  is  contained  in  silver  coin. 

17.  Why  will  a  solution  of  silver  nitrate  curdle  brine  ? 
A  white,  curdy  precipitate  of  silver  chloride  is  formed. 

1 8.  Why  does  writing  with  indelible  ink  turn  black  when 
exposed  to  the  sun,  or  to  a  hot  iron  ? 

By  the  decomposition  of  the  silver  salt  contained  in  the 
ink,  and  consequent  production  of  AgsO,  which  stains 
organic  matter  black. 

1 9.  What  alloys  resemble  gold  ? 
Oreide,  aluminum-bronze,  etc. 

20.  Why  does  a  fish-hook  "  rust  out "  the  line  to  which  it 
is  fastened  ? 

Ferric  oxide  and  ferric  hydrate  act  as  conveyers  of  O, 
absorbing  it  from  the  air  and  giving  it  up  to  organic 
bodies  with  which  they  are  in  contact. 

21.  Why  do  the  nails  in  clap-boards  loosen  ? 

(See  Question  20.) 


126  ANSWEE8  TO  PRACTICAL  QUESTIONS 

22.  Show  that  the  earths  crust  is  mainly  composed  of 
burnt  metals. 

(See  Cooke's  Religion  and  Chemistry?) 

It  consists  largely  of  potassium,  magnesium,  calcium, 
aluminum,  sodium,  etc.,  in  combination  with  O.  These 
compounds  are  the  products  of  combustion. 

The  elements  O,  Si,  Al,  Mg,  Ca,  K,  Na,  Fe,  C,  S,  H, 
Cl  and  N — 13  in  all — probably  make  up  19^r  of  the  earth's 
crust. 

23.  What  kind  of  iron  is  used  for  a  magnet?     For  a 
magnetic  needle  ? 

Steel. 

24.  Why  does  a  tin  pail  so  quickly  rust  out  when  once  the 
tin  is  worn  through  ? 

The  iron  rusts  rapidly  in  the  presence  of  water,  which 
favors  oxidation. 

25.  Why  is  the  zinc  oxide  found  in  New  Jersey  red,  when 
zinc  rust  is  white  ? 

The  oxide  in  New  Jersey  is  colored  by  compounds  of 
iron  and  manganese. 

26.  Should  we  filter  a  solution  of  permanganate  of  potash 
through  paper  ? 

(See  Chemistry ',  page  155,  note.) 

No.     The  salt  will  give  up  O  and  corrode  the  filter. 

27.  Why  is  wood,  cordage,  etc.,  sometimes  soaked  in  a 
solution  of  corrosive  sublimate  ? 

This  salt  possesses  strong  antiseptic  properties. 


IN  CHEMISTRY.  127 

28.  Why  does  the  white  paint  around  a  sink  turn  black  ? 

H2S  is  set  free,  which,  acting  on  the  paint,  forms  lead 
sulphide — the  black  sulphuret  of  lead. 

29.  Why  is  aluminum,  rather  than  platinum,  used  for 
making  the  smallest  weights  ? 

Because  of  its  bulk  as  compared  with  that  of  platinum. 

30.  How  would  you  detect  the  presence  of  iron  particles  in 
black  sand  ? 

By  a  magnet. 

31.  Which  metals  can  be  welded "t 

(See  Philosophy,  page  37.) 
Iron  and  platinum. 

32.  When  the  glassy  slag  from  a  blast-furnace  has  a  dark 
color,  what  does  it  show  ? 

It  might  be  anticipated  that  the  appearance  of  the  slag 
would  convey  to  the  experienced  eye  some  useful  infor- 
mation with  respect  to  the  character  of  the  ore  and  the 
general  progress  of  the  smelting  operation.  A  good  slag 
is  liquid,  nearly  transparent,  of  a  light  grey  color,  and  has 
a  fracture  somewhat  resembling  that  of  limestone.  A 
dark  slag  shows  that  much  of  the  oxide  of  iron  is  escap- 
ing unreduced.  Streaks  of  blue  are  commonly  found 
when  ores  containing  sulphur  are  being  smelted,  possibly 
from  the  presence  of  a  substance  similar  to  ultramarine, 
the  constituents  of  which  are  all  present  in  the  slag. 
Again,  the  slags  obtained  in  smelting  ores  containing  tita- 
nium generally  present  a  peculiar  blistered  appearance. — 
BLOXAM. 


128  ANSWERS  TO  PRACTICAL   QUESTIONS 

33.  In  welding  iron   the  surfaces  to  be  joined  are  some- 
times sprinkled  with  sand.     Explain. 

The  silica  acts  as  a  flux  with  the  oxide  upon  the  sur- 
face and  lays  bare  the  metal  for  welding. 

34.  What  is  the  difference  between  an  alloy  and  an  amal- 
gam ? 

An  amalgam  is  composed  of  mercury  and  some  other 
metal.  An  alloy  consists  of  any  metals  whatever. 

35.  Steel  -articles  are  blued  to  protect  from  rusting,  by 
heating  in  a  sand-bath.     Explain. 

A  thin  coating  of  oxide  is.  formed  on  the  surface  of  the 
metal. 

36.  Give  the  rational  formula  for  copperas  and  white  lead. 

1.  FeSO4    =  FeO,SO3. 

2.  PbCO3  =  PbO,CO2. 

37.  Why  is  Hg  used  for  filling  thermometers! 

(See  Philosophy \  page  235.) 

Because  it  is  fluid  at  all  ordinary  temperatures. 

38.  What  oxide  is  formed  by  the  combustion  0/"Na,  K, 
Zn,  S,  Fe,  Pb,  Cu,   P,  etc.  ?      Which  are  bases  ?      Acids  ? 
Give  the  common  name  of  each. 

(i).  Na2O  is  formed  when  Na  oxidizes  in  dry  air,  or 
oxygen  at  a  low  temperature.  This  takes  up  water  with 
great  avidity,  forming  HNaO  (NaHO),  sodium  hydroxide. 
Na2O2  is  made  when  Na  is  heated  to  200°  C.  HNaO  is 
the  caustic  soda  of  commerce,  and  is  an  alkaline  base. 


IN  CHEMISTRY.  129 

(2).  K  in  a  similar  manner,  depending  upon  the  tem- 
perature, forms  K2O,  K2O2,  and  K2O4.  The  first,  with 
water,  forms  the  ordinary  caustic  potash,  HKO,  of  com- 
merce. It  is  an  alkaline  base. 

(3).  ZnO  is  the  only  known  oxide  of  zinc.  It  forms 
salts. 

(4).  Seven  compounds  of  S  and  O  are  known,  but  only 
two  are  of  interest — the  familiar  anhydrides,  SO2  and 
S03. 

(5).  The  oxides  of  iron  are  four  in  number:  (i)  the 
monoxide,  or  ferrous  oxide,  FeO,  from  which  the  green 
ferrous  salts  are  derived ;  (2)  the  sesquioxide,  or  ferric 
oxide,  Fe2O3,  yielding  the  yellow  ferric  salts;  (3)  the 
magnetic  or  black  oxide,  Fe3O4,  which  does  not  form  any 
definite  salts  ;  (4)  ferric  acid,  H2FeO4,  a  weak  acid,  form- 
ing colored  salts  with  potassium. 

(6).  Pb  forms  two  oxides,  the  monoxide  and  the  di- 
oxide. The  former  is  the  well  known  litharge,  which  is 
the  base  of  the  lead  salts. 

(7).  Cu  has  two  oxides — the  cuprous  (Cu2O)  and 
cupric  (CuO),  both  of  which  form  salts,  thus  giving  rise 
to  two  series,  the  cuprous  and  the  cupric  salts.  The  two 
oxides  are  commonly  known  as  the  red  and  the  black. 

(8).  Phosphorus  forms  two  oxides,  phosphorous  anhy- 
dride (P2O3)  and  phosphoric  anhydride  (P2O5). 

39.  Is  charcoal  lighter  than  H2O  ? 

Charcoal  appears  at  first  sight  to  be  lighter  than 
water,  as  a  piece  of  it  floats  on  the  surface  of  this  liquid ; 
this  is,  however,  due  to  the  porous  nature  of  the  charcoal, 
for  if  it  be  finely  powdered  it  sinks  to  the  bottom  of  the 
water. — ROSCOE. 


13°  ANSWERS  TO  PRACTICAL   QUESTIONS 

40.  Name  the  vitriols. 

The  compounds  of  sulphuric  acid  and  oil  of  vitriol, 
commonly  called  "  the  vitriols,"  are  as  follows : 

1.  Sulphate  of  iron,       Green  vitriol. 

2.  Sulphate  of  copper,  Blue  vitriol. 

3.  Sulphate  of  zinc,        White  vitriol. 

41.  Is  Mg  a  monad  or  a  dyad  ?     Zn.? 

Mg  belongs  to  the  zinc  class  of  metals  which  comprises 
magnesium,  zinc,  cadmium,  and  indium.  These  are  all 
dyads. 

42.  Name  some  dibasic  acid. 
Sulphuric  acid,  carbonic  acid,  etc. 

43.  Name  a  neutral  salt.     An  acid  salt. 

(See  Chemistry,  page  128,  note.) 

44.  Calculate  the  percentage  of  water  contained  in  crystal* 
lized  copper  sulphate.     Sodium  sulphate.     Calcium  sulphate. 
Alum. 

(i).     CuSO«,  sH.O  =  249.5. 

5HaO  =  90. 
Hence,  ,V9°B  =  .36  =  36  %  of  copper  sulphate  is  water. 

(2).    NaaSO,,  ioHaO  =  322. 
ioH2O  =  180. 
Hence,  ||§  =  .55  =  55  %  of  sodium  sulphate  is  water. 

(3).    CaSO4,  2HaO  =  172. 
2H2O  =  36. 
Hence,  rys  =  -20  =  20  %  of  gypsum  is  water. 

(4).    AlaKs,  4SO4  +  24HaO  =  949. 
24H3O  =  432. 
Hence,  -JJf  =  .45  =  45  %  of  potash  alum  is  water. 


IN  CHEMISTRY.  1 3  l 

45.  What  is  the  test  for  Ag  ?     Cu  ? 

Ag  can  be  easily  detected  when  in  solution  by  the  pre- 
cipitation of  the  white  curdy  chloride,  insoluble  in  H2O 
and  HNO3,  and  soluble  in  H3N  :  the  metal  can  be 
obtained  in  malleable  globules  before  the  blowpipe,  and 
is  reduced  from  its  solutions  by  Fe,  Cu,  P,  and  Hg.  Ag 
is  estimated  quantitatively  either  as  the  chloride  or  as 
the  metal. 

Copper  may  be  tested  (i)  by  the  black  insoluble  sul- 
phide ;  (2)  by  the  blue  hydrate  turning  black  on  heating; 
(3)  by  the  deep  blue  coloration  with  ammonia ;  (4)  by 
the  deposition  of  red  metallic  copper  upon  a  bright  sur- 
face of  iron  placed  in  the  solution. 

46.  What   weight  of  crystallized  "tin   salts"  (SnCl2, 
2H2O)  can  be  prepared  from  one  ton  of  metallic  tin? 

Sn  :  SnCla,  2HaO  :  :  2000  Ibs.  :  x. 

118  :     225     :  :  2000  Ibs.  :  x. 

118  x  =  450000  Ibs. 

•*•  =  3813-56  Ibs.  (SnCla,2HaO). 

47.  ioo  parts  by  weight  of  silver  yield  132.8+  parts  of 
silver  chloride.      Given  the  combining  weight  of  chlorine, 
required  that  of  silver. 

x  :  35.5  :  :  ioo  :  32.8  +  . 
328  x  =  3550. 
x  -  108  + . 

48.  What  is  the  composition  of  slacked  lime  1 

(See  Chemistry,  page  137.) 

CaO,H2O. 

49.  How  is  ferrous  sulphate  obtained  ?     How  many  tons 
of  crystals  can  be  obtained  by  the  slow  oxidation  0/230  tons 
of  iron  pyrites  containing  37.5  per  cent,  of  sulphur  ? 

(See  Chemistry,  page  155,  and  Key,  page  60 ;  Question  33.) 


I32  ANSWERS  TO  PRACTICAL  QUESTIONS 

Find  (i)  how  much  S  there  is  in  the  given  weight  of 
iron  pyrites  ;    (2)  how  much  ferrous   sulphate   could  be 
made  from  that  amount  of  S,  if  it  were  all  oxidized, 
(i).    230  tons  x  .375  =  86.25  tons  (S). 

(2).    S  :  FeSO4,  7HaO  :  :  86.25  tons  :  x. 
32  :  278  :  :  86.25  tons  :  x. 

32  x  =  23977.5  tons. 

x  =  749.296  tons  (FeSO«,  7HaO). 

50.  Required  $w  tons  of  soda  crystals ;  what  will  be  the 
weight  of  salt  and  pure  sulphuric  acid  needed'} 

Find  (i)  how  much  Na  there  is  in  500  tons  of  "  soda," 
and  (2)  how  much  NaCl  would  be  needed  to  furnish  that 
amount  of  the  metal  in  case  all  were  utilized. 

(i).    Naa  :  NaaCO3,ioHaO  :  :  x  :  500  tons. 
46  :  286  :  :  x  :  500  tons. 

286  x  =  23,000  tons. 

x  =  80.42-  tons  (Na). 

(2)-    sis  °f  any  amount  of  NaCl  is  Na ;  hence,  to  furnish  80.42  tons  of  Na 
would  require  ||§  x  80.42  tons  =  204.546  tons  (NaCl). 

(3).  By  comparing  the  atomic  weights  of  the  substances  it  will  be  seen 
that  for  46  parts  of  Na  there  must  be  98  of  pure  HaSO«..  ff  x  204.546  tons  = 
435.771  tons  (H,SO«). 

51.  Describe  the  uses  of  lime  in  agriculture. 

(See  Key,  page  51,  Question  12.) 

52.  How  many  tons  of  oil  of  vitriol,  containing  70 per 
cent,  of  pure  acid  (H2SO4),  can  be  prepared  from  250  tons 
of  iron  pyrites,  co?itaining  42  per  cent,  of  sulphur  1     • 

(i).    (See  Question  49.)    250  tons  x  .42  =  105  tons  (S). 

(2).    S  :  H2SO4  :  :  105  tons  :  x. 
32  :      98       :  :  105  tons  :  x. 
32  x  =  10290  tons. 

x  =  321.56  tons  (H2SO«). 

(3).  If  321.56  tons  (H2SO«)  is  70  %  of  the  given  oil  of  vitriol,  the  entire 
amount  would  be  321.56  tons  x  Vr  =  459-28  tons  (oil  of  vitriol). 


IN  CHEMISTRY.  133 

1.  How  would  you  prove  the  presence  of  tannin  in  teal 

By  adding  a  few  drops  of  a  solution  of  ferrous  sulphate. 
This  would  form  a  dark  precipitate  of  iron  tannate. 

2.  How  would  you  test  for  Fe  in  a  solution  ? 

(See  Miller's  Inorganic  Chemistry^  page  525.) 

A  solution  of  nutgalls  will  give  a  bluish-black,  inky  pre- 
cipitate. The  ferrous-  or  proto-salts  are  distinguished  by 
their  light  green  color,  and  by  their  solutions  giving  (i)  a 
white  precipitate,  with  caustic  alkalies ;  (2)  a  light  blue 
precipitate,  with  potassium  ferrocyanide,  which  rapidly  be- 
comes dark  :  whilst  the  ferric-  or  per-salts  are  yellow-col- 
ored, and  their  solutions  yield  (i)  a  deep  reddish-brown 
precipitate,  with  the  caustic  alkalies;  and  (2)  a  deep  blue 
precipitate  (Prussian  blue),  with  potassium  ferrocyanide. 

3.  Why  can  we  settle  coffee  with  an  egg  ? 

The  albumen  of  the  egg  coagulates  by  heat,  and  en- 
tangling the  particles  of  coffee,  mechanically  carries  them 
to  the  bottom. 

4.  How   would  you  show  the  presence  of  starch  in  a 
potato  ?  ^ 

A  solution  of  iodine  will  form  the  blue  iodide  of  starch. 

5.  Why  is  starch  stored  in  the  seed  of  a  plant? 
For  the  growth  of  the  young  plant. 

6.  Why  are  unbleached  cotton  goods  dark-colored? 

Because  of  the  dirt  gathered  in  the  process  of  manufac- 
ture. The  cotton  balls  are  snowy  white. 


134  AN8WEBS  TO  PRACTICAL   QUESTIONS 

7.  Why  do  beans,  rice,  etc.,  swell  when  cooked'} 
By  the  bursting  of  the  starch  granules. 

8.  Why  does  decaying  wood  darken  ? 

By  the  formation  of  humus  which  contains  carbon  in 
excess. 

9.  Why  does  smoke  cure  hams  ? 

The  creosote  of  the  smoke  has  powerful  antiseptic 
properties. 

10.  How  would  you  show  that  C  exists  in  sugar1} 

By  the  experiments  described  in  the  Chemistry  on  page 
117,  note ;  page  190,  note  ;  and  page  191  in  the  formation 
of  caramel. 

1 1.  Why  do  fruits  lose  their  sweetness  when  over-ripe  ? 

(See  Miller's  Organic  Chemistry,  page  875.) 

The  vegetable  acid  contained  in  the  fruit  when  green, 
oxidizes  as  the  ripening  process  continues,  O  being  ab- 
sorbed and  CO  2  evolved.  If  this  continues  too  long,  the 
sugar  itself  becomes  oxidized. 

12.  Why  does  maple-sap  lose  its  sweetness  when  the  leaf 
starts  ? 

The  sugar  of  the  sap  is  applied  to  the  wants  of  the 
growing  tree. 

13.  Should  yeast-cakes  be  allowed  to  freeze  ? 
A  cold  of  32°  will  kill  the  ferment. 


IN  CHEMISTRY.  135 

14.  Why  will  wine  sour  if  the  bottle  be  not  well  corked  ? 

The  presence  of  air  will  cause  the  continuation  of  the 
oxidizing  process  into  the  second  or  acetic  stage. 

15.  Why  can  vinegar  be  made  from  sweetened  water  and 
brown  paper  ? 

The  paper  acts  as  a  ferment,  while  the  sugar  or  mo- 
lasses is  oxidized  into  alcohol  and  thence  into  acetic  acid. 

1 6.  Why  should  the  vinegar-barrel  be  kept  in  a  warm 
place  ? 

Heat  promotes  chemical  change. 

17.  Why  does  "  scalding"  check  the  "working"  of  pre- 
serves ? 

The  ferment  which  causes  the  fermentation  is  killed  by 
the  heat. 

1 8.  Is  the  oxalic  acid  in  the  pie-plant  poisonous  ? 

It  is  neutralized  by  the  alkaline  base,  with  which  it  is 
combined  in  the  plant. 

19.  How  may  ink-stains  be  removed1! 

By  a  solution  of  oxalic  acid,  forming  an  iron  oxalate 
which  is  soluble  in  water,  and  hence  may  be  washed  out. 

20.  Why  is  leather  black  on  only  one  side  ? 

(See  Chemistry^  page  211.) 

The  solution  of  copperas,  which  blackens  the  leather,  is 
applied  on  only  one  side. 


136  ANSWERS  TO  PRACTICAL   QUESTIONS 

21.  Why  do  drops  of  tea  stain  a  knife-blade  ? 

(See  Chemistry,  page  211.) 

The  tannic  acid  of  the  tea  combines  with  the  iron, 
forming  an  iron  tannate.* 

22.  Why  will  not  coffee  stain  it  in  the  same  way  ? 

(See  Miller's  Organic  Chemistry,  page  549.) 

The  modification  of  tannin  contained  in  coffee,  unlike 
that  in  tea,  turns  a  solution  of  ferrous  sulphate  green, 
and  will  not  precipitate  one  of  gelatin. 

23.  Why  does  writing-fluid  darken  on  exposure  to  the 
air? 

(See  Chemistry,  page  262.) 

It  absorbs  O,  the  iron  changing  to  ferric  oxide. 

24.  What  causes  the  disagreeable  smell  of  a  smoldering 
wick  ? 

A  volatile  substance,  termed  acrolein,  is  produced  in 
the  decomposition  of  the  oil. 

25.  Why  does  ink  corrode  steel  pens  ? 

The  free  sulphuric  acid  of  the  ink  combines  with  the 
iron  of  the  pen. 

26.  How  does  a  bird  obtain  the  CaCO3/0r  its  eggshells  ? 

(See  chemistry  of  a  hen's  egg  in  Fireside  Science.) 

A  common  hen's  egg  is  95  per  cent,  carbonate  of  lime, 

*  The  tannic  acid  of  the  tea  tans  the  albumen  of  the  milk  used  in  seasoning 
the  tea,  forming  flakes  of  real  leather.  It  has  been  calculated  that  an  average 
tea-drinker,  in  this  way,  makes  and  drinks  enough  leather  each  year  to  make 
a  pair  of  shoes.  The  albumen  of  milk  uniting  with  the  tannin  acid  of  tea. 
softens  its  flavor.  This  is  generally  preferred  to  the  harsh,  clear  beverage. 


IN  CHEMISTRY.  137 

one  per  cent,  phosphate  of  lime  and  magnesia,  and  two 
per  cent,  animal  matter.  The  shell  would  weigh  over 
100  grains,  so  that  a  hen  laying  100  eggs  in  a  season 
would  require  nearly  i  J  Ibs.  of  CaCO3.  The  hen  must 
in  part  secrete  this  from  her  food,  and  in  part  gather  it 
from  the  sand,  pebbles,  etc.,  she  picks  up  amid  her  inces- 
sant scratching  and  searching. 

27.  Why  will  tallow  make  a  harder  soap  than  lard? 
Tallow  contains  more  palmitin,  and  less  olein,  than  lard. 

28.  Why  does  new  soap  act  on  the  hands  more  than  old  ? 

The  spent  lye,  which  contains  the  excess  of  alkali, 
gradually  separates  from  the  soap,  leaving  only  the  salts 
in  which  the  alkali  is  neutralized  by  the  fatty  acids.  Also 
a  more  complete  combination  takes  place,  whereby  some 
free  alkali  is  taken  up  by  the  acids,  perhaps  before  un- 
combined.  The  former  statement  is  especially  true  in 
the  case  of  soft  or  home-made  soap. 

29.  What  is  the  shiny  coat  on  certain  leaves  and  fruits  ? 
A  species  of  wax  secreted  by  the  plant. 

30.  Why  does  turpentine  burn  with  so  much  smoke  ? 
Because  it  contains  an  excess  of  carbon. 

31.  Why  is  the  nozzle  of  a  turpentine  bottle  so  sticky  ? 

The  turpentine  on  exposure  to  the  air  oxidizes,  turning 
to  rosin. 

32.  Why  does  kerosene  give  more  light  than  alcohol? 

It  contains  more  carbon,  which,  when  heated  in  the 
flame  of  the  burning  H,  gives  out  a  white  light. 


I38  ANSWESS  TO  PRACTICAL  QUESTIONS 

33.  What  is  the  antidote  to  oxalic  acid  ?      Why  ? 
Magnesia  or  chalk,  forming  an  insoluble  oxalate. 

34.  Would  you  weaken  camphor  spirits  with  water  ? 

(See  Chemistry,  page  117.) 

No ;  since  camphor  is  insoluble  in  dilute  alcohol.  The 
principle  is  the  same  as  that  of  the  precipitation  of  lead 
from  dilute  oil  of  vitriol. 

35.  WJiat  is  the  difference  between  rosin  and  resin  ? 

Rosin  is  an  oxidized  resin.  Rosin  is  a  species,  and 
resin  a  genus. 

36.  Why  does  skim-milk  look  blue  and  new  milk  white  ? 

The  globules  of  butter  contained  in  new  milk  reflect 
the  light,  and  so  make  it  look  white  ;  but  when  they  are 
removed,  by  the  separation  of  the  cream,  more  light  is 
transmitted,  and  only  the  blue  is  reflected  to  the  eye. 

37.  Why  does  an  ink-spot  turn  yellow  after  washing  with 
soapl 

The  free  alkali  of  the  soap  combines  with  the  tannic 
acid  of  the  ink,  leaving  the  oxide  of  iron  (ferric  oxide), 
which  stains  the  cloth  yellow. 


140 


ANSWERS  TO  PRACTICAL  QUESTIONS 


IN  CHEMISTRY. 


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ANSWERS 

T  O     T'H  E 

PRACTICAL    QUESTIONS 

IN     THE 

FOURTEEN    WEEKS    IN    HUMAN    PHYSIOLOGY. 


38. — i.  Why  does  not  a  fall  hurt  a  child  as  much  as  it 
does  a  grown  person  ? 

The  bones  of  a  child  are  largely  cartilaginous,  and  so 
do  not  transmit  a  shock,  or  readily  yield  to  a  blow.  They 
are  also  well  padded  with  fat. 

2.  Should  a  young  child  ever  be  urged  to  stand  or  walk  ? 

No ;  bow-legs  are  often  caused  by  the  premature  use 
of  the  lower  limbs  in  standing  or  walking.  Nature  is  the 
best  guide  in  such  matters. 

3.  What  is  meant  by  "  breaking  one's  neck  ?  " 

The  dislocation  of  the  vertebrae  and  consequent  injury 
of  the  spinal  cord. 

4.  Ought  chairs  or  benches  to  have  straight  backs  ? 

The  backs  should  conform  to  the  natural  shape  of  the 
spine.  This  tends  to  prevent  curvatures  and  other  dis- 
tortions of  the  vertebral  column. 


144  ANSWERS  TO  PRACTICAL   QUESTIONS 

5.  Ought  a  child's  feet  to  dangle  from  a  high  chair  ? 

The  position  is  as  unnatural  and  painful  for  a  child  as 
for  a  grown  person. 

6.  Why  can  we  tell  whether  a  fowl  is  young  by  pressing 
on  the  point  of  the  breast-bone  ? 

Because  that  part  of  the  breast-bone  is  not  ossified  in 
a  young  fowl. 

7.  What  is  the  use  of  the  marrow  in  the  bones  ? 

It  contains  the  blood-vessels  carrying  material  for  the 
growth  of  the  bone,  and  also  diffuses  any  shock  which 
the  bone  may  receive. 

8.  Why  is  the  shoulder  so  often  put  out  of  joint  ? 

Because  of  the  shallowness  of  the  socket  in  the 
scapula. 

9.  How  can  you  tie  a  knot  in  a  bone  ? 

By  removing  the  mineral  matter  and  thus  softening  a 
rib-bone,  a  knot  can  be  easily  tied  in  it. 

10.  Why  are  high  pillows  injurious? 

They  elevate  the  head,  and  so  give  an  unnatural  posi- 
tion to  the  spine.  For  the  pads  between  the  vertebrae  to 
assume  their  proper  shape  during  the  night  they  should 
be  relieved  of  all  pressure. 

11.  Is  the  "  Grecian  bend"  a  healthy  position  ? 

The  natural  position  is  the  only  healthy  one.  The 
distortion  known  as  the  "  Grecian  bend  "  contracts  the 
chest,  changes  the  outline  of  the  spine,  and  diminishes 
the  vitality  of  the  system. 


IN  HUMAN  PHYSIOLOGY.  145 

12.  Ought  a  boot  to  have  a  heel-piece  ? 

A  low  and  broad  heel-piece  probably  aids  in  walking  : 
a  narrow  or  high  one  weakens  and  enlarges  the  ankle, 
produces  bunions,  corns,  etc.,  by  throwing  the  weight  for- 
ward upon  the  toes,  and  makes  the  gait  exceedingly 
ungraceful. 

13.  Why  should  one  always  sit  and  walk  erect  ? 

Because  then  all  the  organs  are  in  their  natural 
position. 

14.  Why  does  a  young  child  creep  rather  than  walk  ? 

(See  Physiology,  page  50.) 

Its  bones  not  yet  being  fully  ossified,  nature  teaches  it 
not  to  bear  its  weight  upon  them.  Besides,  it  has  not  yet 
learned  the  difficult  art  of  balancing  itself. 

56. — i.  What  class  of  lever  is  the  foot  when  we  lift  a 
weight  on  the  toes  ? 

The  third  class.  The  ankle-joint  is  the  fulcrum,  the 
weight  is  at  the  toes,  and  the  power  is  in  front  of  the 
ankle,  where  the  muscle  which  lifts  the  toes  (the  extensor 
digitorium)  is  attached  to  the  foot. 

2.  Explain  the  movement  of  the  body  backward  and  for- 
ward, when  resting  tipon  the  thigh-bone  as  a  fulcrum. 

The  weight  is  at  the  center  of  gravity  of  the  head  and 
trunk,  high  above  the  hip  joints,  where  the  fulcrum  is 
situated.  The  flexor  muscles  of  the  thigh  are  the  power, 
and  act  close  to  the  fulcrum.  The  weight  is  sometimes 
directly  over  the  fulcrum,  and  may  be  on  any  side  of  it. 


146  ANSWERS  TO  PRACTICAL   QUESTIONS 

This  seems  to  the  author  to  be  an  example  of  the  first  or 
second  class  of  lever.  Huxley  gives  it  as  an  illustration 
of  the  third  class. 

3.  What  class  of  lever  do  we  use  when  we  lift  the  foot 
while  sitting  down  ? 

The  third  class.  The  fulcrum  is  the  knee-joint ;  the 
weight  is  at  the  center  of  gravity  of  the  foot  and  leg,  and 
the  power  is  applied  by  the  ligament  which  passes  over 
the  patella. 

4.  Explain  the  swing  of  the  arm  from  the  shoulder. 

(See  Physiology,  page  48.) 

The  third  class.  The  fulcrum  is  the  shoulder-joint ; 
the  weight  is  at  the  center  of  gravity  of  the  arm  and 
hand,  and  the  power  is  applied  by  the  biceps  or  triceps 
muscle  at  its  attachment  near  the  elbow. 

5.  What  class  of  lever  is  used  in  bending  our  fingers  ? 

The  fulcrum  is  at  the  junction  of  the  finger  with  the 
palm  ;  the  weight  is  at  the  center  of  gravity  of  the  finger, 
and  may  play  about  the  fulcrum  as  stated  in  second 
question.  It  is  the  third  class  of  lever,  especially  when 
force  is  exerted  at  the  extremity  of  the  fingers. 

6.  What  class  of  lever  is  our  foot  when  we  tap  the  ground 
with  our  toes  ? 

(See  Physiology,  Fig.  14,  £.) 

The  first  class.  The  weight  is  at  the  toe  when  the 
force  is  exerted  ;  the  fulcrum  is  at  the  ankle ;  and  the 
power  is  applied  by  the  gastrocnernius  muscle  at  its 
attachment  to  the  heeh 


IN  HUMAN  PHYSIOLOGY.  147 

7.  What  class  of  lever  do  we  use  when  we  raise  ourselves 
from  a  stooping  position  ? 

The  third  class.  See  second  question.  If  we  are 
attempting  to  lift  a  heavy  burden,  the  bones  act  on  the 
principle  of  the  toggle-joint.  "  When  one  stoops  to  take 
a  heavy  weight  upon  his  back  or  shoulder,  he  puts  both 
the  knee  and  the  hip-joints  into  the  condition  that  the 
toggle-joint  is  when  it  is  bent;  and  then  as  he  straightens 
up,  the  weight  is  raised  by  an  action  of  the  joints  pre- 
cisely similar  to  that  of  the  toggle-joint  in  machinery. 
In  the  case  of  the  knee,  the  straightening  of  the  joints  is 
done  by  the  muscles  on  the  front  part  of  the  thigh,  that 
draw  up  the  knee-pan  with  the  tendon  attached  to  it. 
This  is  using  the  principle  of  the  toggle-joint  in  pressing 
upward.  It  is  also  sometimes  used  in  pressing  downward. 
In  crushing  anything  with  the  heel,  we  give  great  force  to 
the  blow  on  the  principle  of  the  toggle-joint,  by  flexing 
the  knee  and  straightening  the  limb  as  we  bring  down  the 
heel  upon  the  thing  to  be  crushed.  In  pushing  anything 
before  us,  we  bend  the  elbow  as  preparatory  to  the  act, 
and  then  thrust  the  arm  out  straight,  thus  exemplifying 
the  toggle-joint.  The  horse  gives  great  force  to  his  kick 
in  the  same  way.  The  great  power  exerted  by  beasts  of 
draught  and  burden  is  to  be  referred  very  much  to  the 
principle  of  the  toggle-joint.  When  a  horse  is  to  draw  a 
heavy  load,  he  bends  all  his  limbs,  especially  the  hinder 
ones,  and  then  as  he  straightens  them,  he  starts  the  load. 
In  this  case  the  ground  is  the  fixed  block  of  the  mech- 
anism, the  body  of  the  horse  to  which  the  load  is  attached 
is  the  movable  one,  and  his  limbs  are  so  many  toggle- 
joints.  By  this  application  of  the  principle,  we  see 
draught  horses  move  very  heavy  loads." — HOOKER'S  Physi- 


14-  ANSWEMS  TO  PRACTICAL  QUESTIONS 

ology.  "  So  (admitting  fable  to  be  fact),  when  the  farmer, 
in  answer  to  his  petition  for  assistance,  was  commanded 
by  Hercules  to  exert  himself  to  raise  his  wagon  from  the 
pit,  he  placed  his  shoulder  against  the  wheel,  and  draw- 
ing his  body  up  into  a  crouching  attitude,  whereby  all  his 
joints  were  flexed,  and  making  his  feet  the  fixed  points, 
by  a  powerful  muscular  effort,  he  straightened  the  toggle- 
joints  of  his  limbs,  and  the  wheel  was  raised  from  its  bed 
of  miry  clay.  His  horses  at  the  same  moment  extending 
their  joints,  the  heavily  laden  wagon  was  carried  beyond 
the  reach  of  further  detention." — GRISCOM. 

8.  What  class  of  lever  is  the  foot  when  we  walk  ? 

• 
In  the  first  stage  it  is  clearly  the  second  class.     (See 

Physiology,  page  47,  Fig.  18.)  The  fulcrum  is  the  ground 
on  which  the  toes  rest ;  the  power  is  applied  by  the  gas- 
trocnemius  muscle  (see  Fig.  14,  k]  to  the  heel  ;  the 
resistance  is  so  much  of  the  weight  of  the  body  as  is 
borne  by  the  ankle-joint  of  the  foot,  which  of  course  lies 
between  the  heel  and  the  toes. 

9.  Why  can  we  raise  a  heavier  weight  with  our  hand 
when  lifting  with  the  elbow  than  from  the  shoulder  ? 

Because  we  bring  the  fulcrum  nearer  the  power.  In 
the  former  case  it  is  at  the  elbow ;  in  the  latter,  at 
the  shoulder. 

10.  What  class  of  lever  do  we  employ  when  we  are  hop- 
ping, the  thigh-bone  being  bend  up  toward  the  body  and  not 
used? 

In  this  case  the  fulcrum  is  at  the  hip-joint.  The  power 
(which  may  be  assumed  to  be  furnished  by  the  rectus 


IN  HUMAN  PHYSIOLOGY.  149 

muscle  *  of  the  front  of  the  thigh)  acts  upon  the  knee- 
cap ;  and  the  position  of  the  weight  is  represented  by 
that  of  the  center  of  gravity  of  the  thigh  and  leg,  which 
will  lie  somewhere  between  the  end  of  the  knee  and  the 
hip. — HUXLEY. 

n.  Describe  the  motions  of  the  bones  when  we  are  using 
a  gimlet. 

The  radius  rolls  on  the  ulna  at  the  elbow,  while  the 
ulna  rolls  on  the  radius  at  the  wrist.  The  two  combined 
produce  a  free,  rotary  motion. 

12.  Why  do  we  tire  when  we  stand  erect  ? 

(See  Physiology,  page  49.) 

Because  so  large  a  number  of  muscles  must  be  in  con- 
stant  action  to  maintain  this  position. 

13.  Why  does  it  rest  us  to  change  our  work  ? 

We  thereby  bring  into  use  a  new  set  of  muscles. 

14.  Why  and  when  is  dancing  a  beneficial  exercise  ? 

When  dancing  is  performed  out-of-doors,  or  in  a  well- 
ventilated  room  and  at  proper  hours,  it  is  doubtless  a 
beneficial  exercise,  since  it  employs  the  muscles  and 
pleasantly  occupies  the  mind.  Late  at  night,  in  a  heated 
room,  with  thin  clothing  and  exciting  surroundings,  it  is 
simply  a  dangerous  dissipation,  ruinous  to  the  health,  alike 
of  body  and  soul. 


*  This  muscle  is  attached  above  to  the  haunch-bone  or  ileum,  and  below 
to  the  knee-cap.  The  latter  bone  is  connected  by  a  strong  ligament  with  the 
tibia. 


15°  ANSWERS  TO  PRACTICAL   QUESTIONS 

15.  Why  can  we  exert  greater  force  with  the  back  teeth 
than  with  the  front  ones  ? 

(See  Physiology,  page  49.) 

The  lower  jaw  is  a  lever  of  the  second  class.  In  the 
former  case  the  resistance  to  be  overcome,  /".  e.,  the 
weight,  is  situated  much  nearer  the  power. 

1 6.  Why  do  we  lean  forward  when  we  wish  to  rise  from 
a  chair? 

(See  Philosophy,  pages  57-8.) 

In  order  to  bring  the  center  of  gravity  over  the  feet. 

17.  Why  does  the  projection  of  the  heel-bone  make  walking 
easier  ? 

(See  Frontispiece,  and  also  Fig.  18  in  Physiology?) 

It  brings  the  power  further  from  the  fulcrum  or  weight. 

1 8.  Does  a  horse  travel  easier  over  a  flat  than  a  hilly 
country  1 

No.  The  variety  of  travel  in  a  hilly  country,  other 
things  being  equal,  tends  to  rest  the  horse,  and  enable 
him  to  better  endure  the  fatigue  of  the  journey. 

19.  Can  you  move  your  upper  jaw? 

All  the  bones  of  the  face,  except  the  lower  jaw,  are 
firmly  and  immovably  articulated  with  one  another  and 
with  the  cranium. — LEIDY. 

20.  Are  people  naturally  right  or  left-handed? 

•Many  persons  are  naturally  either  right  or  left-handed  ; 
but  most  can  and  should  learn  to  use  either  hand  with 
equal  facility. 


IN  HUMAN  PHYSIOL OGY.  IS1 

21.  Why  can   so  few  persons    move -their  ears  by  if  he 
muscles  ? 

Perhaps,  because  of  lack  of  practice  ;  more  probably, 
however,  the  muscles  (see  Physiology,  p.  65  and  Fig.  14) 
are  developed  in  few  persons. 

22.  Is  the  blacksmith's  right  arm  healthier  than  the  left? 

By  no  means.  Strength  is  not  essential  to  health. 
The  right  arm  may  be  stronger,  but  the  functions  of  the 
left  may  be  as  active  and  well-performed. 

23.  Boys  often,  though  foolishly,  thrust  a  pin  into  the 
flesh  just  above  the  knee.      Why  is  it  not  painful  1 

The  muscles  of  the  leg  there  end  in  tendons,  which  are 
insensible. 

24.  Will  ten  minutes  practice  in  a  gymnasium  answer  for 
a  day's  exercise  ?  . 

Spasmodic  or  violent  exercise  is  not  beneficial.  It 
should  be  comparatively  quiet,  gentle,  and  continuous  to 
produce  the  best  effect.  Moreover,  the  vitalizing  influ- 
ences of  the  sun  and  pure  air  demand  that  we  should 
exercise  out-of-doors. 

25.  Why  would  an  elastic  tendon  be  unfitted  to  transmit 
the  motion  of  a  muscle  ? 

Force  would  be  lost  by  its  transmission  through  an 
elastic  medium. 

26.  When  one  is  struck  violently  on  the  head,  why  does 
he  instantly  fall  ? 

The  body  is  kept  erect  only  by  the  constant  exercise 


152  ANSWERS  TO  PRACTICAL    QUESTIONS 

of  many  muscles.  These  perform  their  functions  through 
the  unconscious  action  of  the  brain  and  spinal  cord.  A 
blow  paralyzes  the  nervous  system,  the  muscles  at  once 
cease  to  act,  and  the  body  falls  by  its  weight. 

27.  What  is  the  cause  of  the  difference  between  light  and 
dark  meat  in  a  fowl? 

The  amount  of  blood  which  circulates  through  differ- 
ent parts  of  the  body.  The  organs  of  a  fowl  which  are 
used  the  most  become  the  darkest. 

79.     i.  If  a  hair  be  plucked  out,  will  it  grow  again  ? 

Yes.  A  new  hair  will  always  grow  out  so  long  as  the 
papilla  at  the  bottom  of  the  follicle  remains  uninjured. 

2.  What  causes  the  hair  to  "  stand  on  end"  when  we  are 
frightened? 

(See  Physiology,  page  65.) 

"  Many  of  the  unstriated  muscular  fibres  from  the  true 
skin  pass  obliquely  down  from  the  surface  of  the  dermis 
to  the  under  side  of  the  slanting  hair-follicles.  The  con- 
traction of  these  fibres  erects  the  hairs,  and  by  drawing 
the  follicles  to  the  surface  and  drawing  in  a  little  point 
of  the  skin,  produces  that  roughness  of  the  integument 
called  "goose-skin,"  or  Cutis  Anserina.  The  standing 
on  end  of  the  hair  of  the  head,  as  the  result  of  extreme 
fright,  may  be  partly  due  to  the  contraction  of  such 
fibres,  as  well  as  to  the  action  of  the  occipito-frontalis 
muscle." — CUTTER. 

3.  Why  is  the  skin  roughened  by  riding  in  the  cold? 

(See  Physiology ',  page  65  ;  also  Answer  to  Question  2.) 


IN  HUMAN  PHYSIOLOGY.  153 

4.  Why  is  the  back  of  a  washer-woman's    hand  less 
water-soaked  than  the  palm  ? 

The  difference  depends  upon  the  relative  abundance 
of  the  oil-glands  in  different  parts  of  the  body. 

5.  What  would  be  the  length  of  the  perspiratory  tubes 
in  a  single  square  inch  of  the  palm,  if  placed  end  to  end? 

(See  Physiology,  page  72.    2,800  x  TV  in.  =2££e  in.=  14  ft.  7  in.— Answer.) 

6.  What  colored  clothing  is  best  adapted  to  all  seasons  ? 

Light-colored  clothing  is  cooler  in  summer  and  warmer 
in  winter. 

(See  Physiology,  page  77  ;  Natural  Philosophy,  page  246.) 

7.  What  is  the  effect  of  paint  and  powder  on  the  skin  ? 

They  fill  the  pores  of  the  skin,  and  thus  prevent  the 
passage  of  the  perspiration.  Moreover,  they  often  con- 
tain substances  which  are  poisonous,  and  being  carried 
in  by  the  absorbents  cause  disease. 

(See  Physiology,  page  73.) 

8.  Is  water-proof  clothing  healthful  for  constant  wear  ? 

No.  It  retains  the  insensible  perspiration  by  which 
waste  matter  is  being  constantly  thrown  off  from  the 
system. 

9.  Why  are  rubbers  cold  to  the  feet  ? 

They  retain  the  insensible  perspiration.  The  moisture 
which  gathers  absorbs  the  heat  of  the  feet,  and  readily 
conducts  it  from  the  body. 


154  ANSWERS   TO  PRACTICAL    QUESTIONS 

10.  Why  does  the  heat  seem  oppressive  when  the  air  is 
moist  ? 

In  the  moisture-laden  atmosphere,  the  evaporation  of 
the  insensible  perspiration  from  the  surface  of  the  body 
goes  on  slowly.  The  heat,  which  would  otherwise  pass 
off  through  the  pores,  is  retained  in  the  system. 

1 1.  Why  is  friction  of  the  skin  invigorating  after  a  cold 
bath? 

The  friction  produces  heat,  expands  the  veins,  etc.,  on 
the  surface,  and,  calling  the  blood  in  that  direction,  pro- 
duces a  vigorous  circulation.  In  other  words,  it  causes  a 
reaction.* 

(See  Physiology,  page  75.) 

12.  Why  does  the  hair  of  domestic  animals  become  rough- 
ened in  winter  ? 

(See  Question  2.) 

The  effect  is  beneficial,  since  more  air — a  non-conduc- 
tor of  heat — is  retained  by  the  hair,  and  thus  the  rough 

*  "  Strength  in  the  living  body  is  maintained  by  the  full  but  natural  exercise 
of  each  organ ;  and  as  we  have  seen,  the  actions  of  these  portions  of  the  ner- 
vous system  is  made  dependent  upon  influences  conveyed  to  them  by  the 
sensitive  nerves  distributed  over  the  various  parts  of  the  body.  And  among 
these  the  nerves  passing  to  the  skin  are  the  chief.  The  full  access  of  all 
healthful  stimuli  to  the  surface,  and  its  freedom  from  all  that  irritates  or  im- 
pedes its  functions,  are  the  first  external  conditions  of  the  normal  vigor  of  this 
nervous  circle.  Among  these  stimuli,  fresh  air  and  pure  water  hold  the  first 
place.  Sufficient  warmth  is  second.  The  great,  and  even  wonderful  advan- 
tages of  cleanliness  are  partly  referable  to  the  direct  influence  of  a  skin 
healthily  active,  open  to  all  the  natural  stimuli,  and  free  from  morbid  irrita- 
tion, upon  the  nerve-centres  of  which  it  is  the  appointed  excitant.  This  influ- 
ence is  altogether  distinct  from  those  cleansing  functions  which  the  healthy 
skin  performs  for  the  blood ;  and  in  any  just  estimate  of  its  value  is  far  too 
important  to  be  overlooked."— HINTON. 


7JV  HUMAN  PHYSIOLOGY.  155 

winter-coat  of  an  animal  is  warmer  than  its  smooth  sum- 
mer-coat. 

13.  Why  do  fowls  shake  out  their  feathers  erect  before 
they  perch  for  the  night  ? 

(See  Question  12.) 

This  is  a  wise  provision  of  Nature  to  protect  the  fowl 
against  the  chilliness  of  the  night.  More  air  is  confined 
by  the  roughened  feathers,  and  thus  the  internal  heat  of 
the  bird  is  prevented  from  radiating. 

14.  How  can  an  extensive  burn  cause  death  by  congestion 
of  the  lungs  ? 

The  insensible  perspiration  is  stopped  upon  the  burned 
surface,  and  the  excretions  are  sent  to  the  lungs,  which 
are  overworked  and  overloaded  by  the  excess. 

(See  Physiology,  page  74.) 

15.  Why  do  we  perspire  so  profusely  after  drinking  cold 
water  ? 

The  vital  organs  being  chilled  for  an  instant,  the  blood 
is  sent  to  the  surface,  a  reaction  is  produced,  the  skin 
acts  more  vigorously  as  an  excretory  organ,  and  the 
insensible  perspiration  is  thrown  off  more  rapidly. 

1 6.  What  are  the  best  means  of  preventing  skin  diseases, 
colds,  and  rheumatism  ? 

The  skin  should  be  kept  in  a  healthy  state  by  bathing, 
rubbing,  etc.  Exposure  to  sudden  changes  of  tempera- 
ture should  be  avoided  as  far  as  possible.  Flannel 


156  ANSWERS   TO  PRACTICAL   QUESTIONS 

worn  next  the  skin,  in  all  seasons  of   the   year,  is  an 
excellent  precaution  against  unavoidable  exposure. 

17.  What  causes  the  difference  between  the  hard  hand  of 
a  blacksmith  and  the  soft  hand  of  a  woman  ? 

The  varying  thickness  of  the  cuticle. 

(See  Physiology,  page  62.) 

1 8 .  Why  should  a  painter  avoid  getting  paint  on  the  palm 
of  his  hand? 

(See  Physiology,  page  73.) 

19.  Why  should  we  not  use  the  soap  or  soiled  towel  at  a 
hotel? 

Because  of  the  danger  of  contracting  disease  through 
the  absorbents  01  the  skin.  (See  Physiology,  p.  73.) 
There  is  a  similar  danger  in  using  a  hair-brush  or  a 
comb  at  a  barber  shop. 

20.  Which  teeth  cut  like  a  pair  of  scissors  ? 

The  "back-teeth,"  as  we  commonly  call  them,  when 
moved  laterally,  cut  somewhat  in  this  way.  In  chewing 
the  food  all  the  "tront  teeth"  act  like  scissors,  as  may 
be  readily  seen  by  noticing  their  movements. 

2 1 .  Which  like  ct  chisel  ? 

The  incisors,  or  four  front  teeth  of  each  jaw,  have 
knife  edges ;  the  canine  teeth  have  wedge-shaped  edges ; 
the  bicuspids  and  molars  have  broader  crowns.  We  can 
work  the  jaws  so  as  to  make  the  front-teeth  either  pierce 
like  wedges  or  cut  like  scissors. 


IN  HUMAN  PHYSIOLOGY.  157 

22.  Which  should  be  clothed  the  warmer,  a  merchant  or 
a  farmer  ? 

The  merchant  is  liable  to  more  sudden  and  violent 
changes  of  temperature,  and  his  body  is  less  likely  to  be 
hardened  by  exposure  and  habit  to  resist  them. 

23.  Why  should  we  not  crack  nuts  with  our  teeth  ? 

The  brittle  enamel  is  very  liable  to  crack,  and  once 
broken  can  never  be  restored. 

24.  Do  the  edges  of  the  upper  and  lower  teeth  meet1} 

(See  Question  21.) 

25.  When  fatigued,  would  you  take  a  cold  bath  ? 

Certainly  not.  The  system  is  not  vigorous  enough  to 
produce  a  reaction,  and  the  effect  might  be  dangerous. 

26.  Why  is  the  outer  surface  of  a  kid  glove  finer  than  the 
inner  ? 

This  illustrates  the  difference  in  texture  between  the 
cutis  and  cuticle ;  the  dermis  and  epidermis. 

27.  Why  will  a  brunette  endure  the  sun's  rays  better  than 
a  blonde  ? 

(See  Physiology,  page  63.) 

The  skin  is  perhaps  of  a  coarser  texture,  and  not  so 
sensitive  to  heat.  May  it  not  be  also  that  the  black  pig- 
ment absorbs  the  heat  and  radiates  it  again  rather  than 
transmits  it  directly  to  the  internal  organs  ?  It  has  also 
been  suggested  that  there  is  an  increased  flow  of  blood 
in  the  darker  skin,  and  hence  increased  perspiration. 


158  ANSWERS  TO  PRACTICAL    QUESTIONS 

28.  Does  patent-leather  form  a  healthful  covering  for  the 
feet? 

No.     The  pores  of  the  leather  are  partly  rilled,  and 
hence  the  insensible  perspiration  is  largely  restrained. 

29.  Why  are  men  more  frequently  bald  than  women  ? 

This  is  the  effect  of  the  close,  unventilated  head-cover- 
ing commonly  worn  by  men. 

30.  On  what  part  of  the  head  does  baldness  commonly 
occur  ? 

On  that  part  most  fully  covered  by  the  hat  or  cap. 

31.  What  does  the  combination  in  our  teeth  of  canines 
and  grinders  suggest  as  to  the  character  of  our  food? 

That  we  are  to  eat  a  mixed  diet  of  vegetable  and  ani- 
mal food.* 


*  u  The  question  of  the  use  of  animal  or  vegetable  food  may  well  be  re- 
mitted to  the  arbitrament  of  nature,  as  expressed  in  the  desires  ;  by  which  it 
would  be  victoriously  decided,  in  all  such  climates  as  ours,  in  favor  of  the 
flesh-eater.  But  the  sufficiency  of  vegetable  food,  if  widely  varied,  to  main- 
tain health  and  even  strength,  is  not  to  be  questioned,  for  those  who  like  it. 
When  we  hear  that  the  ancient  Persians  lived  a  good  deal  on  water-cress,  we 
naturally  connect  in  our  minds  their  physical  inferiority  with  the  poverty  of 
their  diet ;  but  finding,  on  the  other  hand,  that  the  Romans,  in  the  best  period 
of  the  Republic,  largely  sustained  themselves  on  turnips,  and  that  degeneracy 
came  in  as  turnips  went  out,  we  are  compelled  to  reconsider  our  opinion.  In 
brief,  an  exclusively  vegetable  food  may  be  best  suited  to  those  by  whom  it 
really  is  preferred.  Children  in  this  respect  exhibit  the  greatest  difference ; 
some,  with  manifest  advantage,  eat  meat  in  large  quantity — others  can  hardly 
be  prevailed  on  to  taste  it,  and  yet  retain  perfect  vigor.  Similar  differences, 
in  all  probability,  exist  among  adults;  but  a  vegetarianism  self-imposed 
against  the  promptings  of  desire,  would  tend,  as  a  vigorous  writer  says,  to 
make  us  l  not  the  children,  but  the  abortions  of  Paradise.'  "— HINTON. 


IN  HUMAN  PHYSIOLOGY.  159 

32.  Is  a  staid,  formal  promenade  suitable  exercise? 

No.  There  is  an  intimate  relation  between  the  brain 
and  the  muscles.  The  mind  should  be  pleasantly  em- 
ployed to  obtain  the  full  effect  of  any  exercise.  The 
sports  of  children  are  often  the  very  perfection  of  health- 
ful gymnastic  exercises  ?  * 

33.  Is  there  any  danger  in  changing  the  warm  clothing  of 
pur  daily  wear  for  the  thin  one  of  a  party  ? 

Very  great.  The  body  is  not  as  well  protected  as 
usual  against  a  sudden  change  of  temperature,  as  in 
going  from  a  heated-room  to  the  carriage,  and  a  cold  is 
often  the  consequence.  This  may  lay  the  foundation  of, 
or  prepare  the  way  for,  fatal  disease. 

34.  Should  we  retain  our  overcoat,  shawl,  or  furs,  when 
we  come  into  a  warm  room  ? 

No.  The  body  will  become  over-heated,  the  pores  be 
opened,  and  the  skin  be  rendered  susceptible  to  the 
change  of  temperature  when  we  return  into  the  open 
air. 

35.  Which  should  bathe  the  oftener,  students  or  out-door 
laborers  ? 

*  "  The  mental  operations,  like  all  others,  are  connected  with  changes  in 
the  material  of  the  body.  In  all  our  consciousness  the  chemical  tendencies 
of  the  substance  of  the  brain  come  into  play,  and  thus  a  chain  of  action  is  set 
up  which  extends  throughout  the  system.  The  influence  of  these  brain- 
changes  is  felt  wherever  a  nerve  travels,  and  modifies,  invigorates,  or  de- 
praves the  action  of  every  part.  Experience  gives  ample  proof  of  this  fact  to 
every  one,  as  in  the  sudden  loss  of  appetite  a  piece  of  bad  news  will  cause,  or 
in  the  watering  of  the  mouth  excited  by  the  thought  of  food.  And  the  history 
of  disease  abounds  in  evidence  of  a  similar  kind :  hair  becoming  gray  in  a 
single  night  from  sorrow,  milk  poisoning  an  infant  from  an  attack  of  passion 
in  the  nurse,  permanent  discoloration  of  the  skin  from  terror,  are  among  the 
instances  on  record."— HINTON. 


l6o  ANSWERS    TO  PRACTICAL    QUESTIONS 

This  depends  entirely  on  circumstances — the  amount 
of  exercise,  freedom  and  character  of  perspiration,  state 
of  the  system,  etc.  Each  case  must  be  decided  by  it- 
self. 

36.  Is  abundant  perspiration  injurious  ? 

No.  It  removes  impure  matter  from  the  system,  and 
hence  may  be  beneficial.  It  may,  however,  weaken  the 
body,  and  frequent  hot  baths  should  therefore  be  taken 
only  on  suitable  medical  advice. 

99. — i.  What  is  the  philosophy  of  the  "change  of  voice" 
in  a  boy  ? 

Up  to  the  age  of  fourteen  or  fifteen,  there  is  little  or 
no  difference  in  point  of  size  between  the  larynx  of  a 
boy  and  that  of  a  girl;  but  subsequently  the  former 
grows  proportionately  larger,  so  that  at  last,  in  the  adult 
male,  the  vibrating  parts  or  vocal  cords  are  necessarily 
longer  than  in  the  female.  They  are  also  undoubtedly 
thicker,  perhaps  even  coarser  in  structure.  From  all  these 
circumstances  the  adult  male  voice  is  stronger,  louder,  and 
of  lower  pitch  than  the  weaker  and  higher  vocal  range 
accomplished  by  the  female  larynx. 

The  cause  of  the  difference  in  quality  of  the  voice, 
known  as  its  timbre,  is  not  well  known  ;  but  it  must 
undoubtedly  be  dependent  on  physical,  that  is  to  say, 
structural  peculiarities  in  some  part  of  the  laryngeal 
apparatus. 

The  production  of  the  different  notes  within  the  com- 
pass of  any  one  individual  depends  upon  alterations  in 
the  length  and  state  of  tension  of  the  vocal  cords,  and  on 
their  degree  of  proximity  or  separation  from  one  another 


IN  HUMAN  PHYSIOLOGY.  id 

The  higher  notes  require  the  vocal  cords  to  be  compara- 
tively shorter,  tighter,  and  more  closely  approximated 
together;  whilst  the  lower  notes  demand  opposite  condi- 
tions. A  high  note,  furthermore,  implies  greater  rapidity 
in  the  movement  of  the  air  through  the  glottis  ;  but  the 
quantity  of  air  passing  is  larger  during  the  production  of 
a  low  note. 

The  volume  or  loudness  of  the  voice  depends  mainly 
on  the  combination  of  quantity  of  air  with  greater  force 
of  expulsion.  Loudness,  with  clearness,  also  demands  a 
peculiar  resonance  up  in  the  nasal  cavities  and  sinuses. 
Lastly,  the  unnatural  or  falsetto  voice  seems  also  to  be 
produced  by  some  tensive  change  effected  in  the  upper 
part  of  the  pharynx  at  the  back  of  the  nose  :  hence  it  is 
called  by  singers  the  head  voice,  in  contradistinction  to  the 
ordinary,  or  chest  voice. — MARSHALL. 

2.  Why  can  we  see  our  breath  on  a  frosty  morning? 
The  vapor  of  the  breath  is  condensed  by  the  cold  air. 

3.  When  a  law  of  health  and  a  law  of  fashion  conflict, 
which  should  we  obey  ? 

It  depends,  of  course,  whether  we  prefer  to  be  fashion- 
able or  to  be  healthy,  to  obey  man  or  God.  With  too 
many  people  the  former  is  of  far  greater  importance,  and 
in  selecting  an  article  of  dress,  few  ask  or  think  about 
the  latter.  The  consequence  is  seen  in  the  weakened 
frame,  the  prevalence  of  disease,  and  the  shortened  life. 
God's  laws  written  in  our  bodies  cannot  be  violated  with 
impunity. 

4.  If  we  use  a  "  bunk  "  bed,  should  we  pack  away  the 
clothes  when  we  first  rise  in  the  morning  ? 

No.     They  should  first  be  thoroughly  aired. 


1 62  ANSWERS  TO  PRACTICAL  QUESTIONS 

5.  Why  should  a  clothes-press  be  well  ventilated  ? 

The  clothes  naturally  contain  the  products  of  the 
insensible  perspiration,  which  passing  off,  pollute  the 
air  of  the  closet. 

6.  Should  the  weight  of  our  clothing  hang  from  the  waist 
or  the  shoulder  ? 

From  the  shoulder,  so  as  to  avoid  the  constriction  of 
the  compressible  organs  in  the  abdomen. 

7.  Describe  the  effects  of  living  in  an  over-heated  room. 

(i).  The  body  becomes  more  sensitive  to  change,  and 
the  susceptibility  to  colds  is  greatly  increased :  (2)  the 
dry,  heated  air  abstracts  the  moisture  from  the  skin,  ren- 
dering it  dry,  hard,  and  incapable  of  performing  its  nor- 
mal functions. 

8.  What  habits  impair  the  power  of  the  lungs  ? 

Above  all  others,  those  qf  a  leaning  posture,  tight- 
lacing,  and  ill-ventilation. 

9.  for  full,  easy  breathing  in  singing,  should '  >  we  use  the 
diaphragm  and  lower  ribs  or  the  upper  ribs  alone  ? 

Nearly  all  the  inspirations  are  effected  by  the  move- 
ments of  the  diaphragm  and  the  inferior  ribs  only.  From 
time  to  time  a  deeper  and  more  complete  inspiration 
causes  the  thorax  to  rise,  not  simultaneously,  but  succes- 
sively at  the  base,  then  at  the  apex.  In  the  first  case  the 
respiration  is  diaphragmatic ;  when  the  lower  and  middle 
ribs  are  raised,  it  is  termed  lateral;  and  lastly,  when  the 
first  rib  and  clavicle  take  part  in  the  movement,  it  is 


IN  HUMAN  PHYSIOLOGY.  163 

costo-superior  or  clavicular.  In  diaphragmatic  respira- 
tion, as  M.  Mandl  has  observed,  the  larynx  is  immovable, 
the  inspiration  is  easy,  without  effort,  and  permits  exer- 
tion in  singing  or  in  gymnastics  for  a  long  time  and 
without  fatigue.  On  the  contrary,  persons  who  respire 
principally  by  the  upper  ribs  are  easily  fatigued,  and  very 
soon  out  of  breath.  This  is  seen  in  women  when  the 
corset  compresses  the  base  of  the  chest,  and  in  singers 
who  adopt,  on  erroneous  principles,  the  bad  habit  of 
clavicular  respiration.  In  this  last  method  of  inspiration 
the  larynx  is  drawn  down  by  the  contraction  of  the 
external  muscles,  and  its  action  becomes  painful.  The 
effort  of  the  inspiratory  muscles  rapidly  induces  fatigue, 
and  the  inspiration,  always  incomplete,  becomes  also 
more  frequent.  Diaphragmatic  respiration  is  practised 
by  mountaineers,  gymnasts,  and  skilful  singers — a  habit 
induced  either  by  instinct,  or  a  well-directed  education. — 
Wonders  of  the  Human  Body. 

10.  Why  is  it  better  to  breathe  through  the  nose  than  the 
mouth  ? 

The  air  passing  through  the  nostrils  becomes  filtered 
of  its  coarse  impurities,  and  the  chill  is  taken  off  before  it 
strikes  against  the  tender,  mucous  surfaces  of  the  larynx. 

1 1.  Why  should  not  a  speaker  talk  while  returning  home 
on  a  cold  night  after  a  lecture  ? 

The  cold  air  will  strike  against  the  vocal  apparatus 
when  inflamed  and  peculiarly  sensitive. 

12.  What  part  of  the  body  needs  the  loosest  clothing  ? 

The  abdomen  ;  because  of  the  delicate  organs  within, 
unprotected  by  a  bony  covering. 


1 64  ANSWERS   TO  PRACTICAL   QUESTIONS 

13.  What  part  needs  the  warmest  ? 

The  feet,  because  they  are  furthest  from  the  center  of 
heat  and  motion  and  most  exposed  to  cold  and  wet :  and 
the  neck  and  shoulders,  since  here  are  located  the  deli- 
cate organs  of  voice  and  respiration. 

14.  Why  is  a  "  spare  bed  "  generally  unhealthy  ? 
Because  it  is  apt  to  be  damp  and  unventilated. 

15.  Is  there  any  good  in  sighing? 

(See  Physiology,  page  91.) 

It  probably  brings  up  the  "  arrears  "  of  respiration. 

1 6.  Ought  a  hat  to  be  thoroughly  ventilated  ?     How  ? 

Certainly,  as  the  heated,  foul  air  is  injurious.  A  single 
hole  at  the  top  is  quite  insufficient  for  ventilation. 
Several  openings  should  be  made  on  the  sides  near  the 
band. 

1 7.  Why  do  the  lungs  of  people  who  live  in  cities  become 
of  a  gray  color. 

Probably  because  of  the  deposition  of  carbonaceous 
particles  which  penetrate  the  substance  of  the  tissues. 
The  coloring  is  permanent,  like  tattooing,  where  india- 
ink  is  pricked  beneath  the  skin. 

1 8.  How  would  you  convince  a  person  that  a  bed-room 
should  be  aired  ? 

Take  him  from  the  fresh,  pure,  invigorating  out-door 
atmosphere  into  the  close,  depressing  air  of  the  bed-room, 
when  first  vacated  in  the  morning,  and  his  sense  of  smell 
will  satisfy  him  of  the  need  of  ventilation. 


IN  HUMAN  PHYSIOLOGY.  1 65 

19.  What  persons  are  most  liable  to  scrofula,  consump- 
tion, etc. 

(See  Physiology,  pages  94-98.) 

The  victims  of  lung-starvation. 

20.  If  a  person  is  plunged  under  water,  will  any  enter 
his  lungs  ? 

No.  The  epiglottis  will  close  involuntarily  and  pre- 
vent the  admission  of  water. 

21.  Are  bed-curtains  healthy  1 

No.  They  prevent  the  free  circulation  of  the  air  and 
confine  the  waste  products  thrown  off  from  the  body. 

22.  Why  do  some  persons  take  "short  breaths"  after  a 
mean 

The  distention  of  the  stomach  prevents  the  free  action 
of  the  lungs.  If  such  persons  are  not  given  to  gluttony, 
the  lungs  are  small  or  the  other  organs  misplaced. 

23.  What  is  the  special  value  of  public  parks  ? 

They  bring  fresh  air,  sunshine,  green  grass  and  trees 
within  the  reach  of  all.  They  are  truly  the  "  breathing- 
holes  of  a  city."  They  are  thus  of  incalculable  benefit 
both  on  account  of  their  sanitary  and  moral  influence. 

24.  Can  a  per  son  become  used  to  bad  air,  so  that  it  will 
not  injure  him  ? 

The  system  may  come  to  endure  without  complaint,  but 
never  fails  to  inflict  full  punishment  for  the  infraction  of 
nature's  laws. 


1 66 


ANSWERS  TO  PRACTICAL   QUESTIONS 


25.  Why  do  we  gape  when  we  are  sleepy  ? 

(See  Question  15.) 

The  stretching  of  the  nerves  may  perhaps  serve  to 
restore  the  equilibrium  of  the  nervous  influence,  disturbed 
by  the  attention  being  fixed  during  the  day  upon  some 
absorbing  occupation. 

26.  Is  a  fashionable  waist  a  model  of  art  in  sculpture  or 
painting  ? 

The  Venus  of  Milo,  in  the  Louvre  at  Paris,  is  the  beau- 
ideal  of  symmetry  and  beauty,  yet  the  form  indicates  not 
a  "wasp-waist,"  but  the  full,  free,  flowing  outlines  of 
nature.  The  sculptor  and  painter  in  copying  the  human 
figure  can  make  no  improvement  on  its  Divine  maker. 

27.  Should  a  fire-place  be  closed*? 

(See  Physiology,  page  100.) 

No.     It  is  a  most  efficient  means  of  ventilation. 

28.  Why  does  embarrassment  or  fright  cause  a  stammerer 
to  stutter  still  more  painfully  ? 

Stuttering  is  mainly  a  nervous  disorder,  and  hence  any 
excitement  tends  to  increase  the  impediment  of  the 
speech. 

29.  In  the  organs  of  voice,  what  parts  have  somewhat  the 
same  office  as  the  case  of  a  violin  and  the  sounding-board  of 
a  piano? 

(See  Philosophy,  page  176.) 

The  pharynx,  the  mouth,  and  the  nasal  passages  all  act 
by  resonance  to  modify  the  voice. 


/2V  HUMAN  PHYSIOLOGY.  167 

129. — i.  Why  does  a  dry,  cold  atmosphere  favorably 
affect  catarrh  ? 

It  tends  to  diminish  inflammation  in  the  mucous  mem- 
brane lining  the  nose  and  nasal  passages. 

2.  Why  should  we  put  on  extra  covering  when  we  }ie 
down  to  sleep  ? 

The  respiration  and  the  circulation  are  then  less  active. 
The  fire  in  our  corporeal  stoves  being  low,  we  need  extra 
covering  to  preserve  the  warmth  of  the  body. 

3.  Is  it  well  to  throw  off  our  coats  or  shawls  when  we 
come  in  heated  from  a  long  walk  ? 

No.  We  rather  need  to  put  on  extra  clothing  at  such 
times  to  keep  the  body  from  cooling  too  rapidly.  The 
best  hygienic  teachers  commend  the  throwing  of  a  shawl 
about  the  shoulders  whenever  we  sit  down  to  rest  after 
fatiguing  labor. 

4.  Why  are  close-fitting  collars  or  neck-ties  injurious  ? 
They  impede  both  respiration  and  circulation. 

5.  Which  side  of  the  heart  is  the  more  liable  to  inflam* 
mation  ? 

The  left ;  since  that  contains  the  red  blood  just  oxygen- 
ated in  the  lungs. 

6.  What  gives  the  toper  his  red  nose  ? 

(See  Physiology,  pages  125  and  173.) 

The  congested  state  of  the  capillaries. 


1 68  ANSWERS  TO  PRACTICAL   QUESTIONS 

7.  Why  does  not  the  arm  die  when  the  surgeon  ties  the 
principal  artery  leading  to  it  ? 

The  anastomoses  of  the  arteries  enable  a  collateral 
circulation  to  be  established,  whereby  blood  is  supplied 
to  the  arm. 

8.  When  a  fowl  is  angry,  why  does  its  comb  redden  ? 

Because  an  extra  quantity  of  blood  is  thrown  into  that 
part  of  the  body. 

9.  Why  does  a  fat  man  endure  cold  better  than  a  lean 
one? 

Fat  is  a  good  non-conductor  of  heat,  and  helps  to  pre- 
serve the  uniform  temperature  of  the  body. 

10.  Why  does  one  become  thin  during  a  long  sickness  ? 

By  absorption,  the  fat  of  the  body  is  taken  up  and 
used  to  supply  the  wants  of  the  system.  The  old  flesh 
being  renewed  with  new,  vigorous  material,  after  such  a 
wasting  sickness,  a  person  often  has  better  health  than 
previous  to  it. 

11.  What  would  you  do  if  you  should  come  home  "wet 
to  the  skin  ?" 

One  should  (i)  go  into  a  warm  room;  (2)  remove  all 
wet  garments  ;  (3)  if  chilled,  take  a  hot,  full-  or  foot-bath, 
and  by  gentle  friction  restore  the  circulation  ;  (4)  put  on 
dry  clothing. 

12.  When  the  cold  air  strikes  the  face,  why  does  it  first 
blanch  and  then  flush  ? 


IN  HUMAN  PHYSIOLOGY.  169 

The  muscles  and  blood-vessels  of  the  surface  are  con- 
tracted by  the  cold,  and  the  blood  is  driven  back  toward 
the  heart.  The  reaction  which  ensues  forces  the  blood 
again  toward  the  skin,  and  this  flushes  with  the  incoming 
tide.  The  face  is  therefore  first  whitened  and  then  red- 
dened. 

13.  What  must  be  r'he  effect  of  tight  lacing  upon  the  circu- 
lation of  the  blood  ? 

It  must,  by  contracting  the  blood-vessels,  impede  the 
flow  of  the  blood,  and  by  decreasing  the  quantity  fur- 
nished the  various  organs,  injure  their  action.  Thus, 
finally,  it  will  impair  the  quality  of  the  blood. 

14.  Do  you  know  the  position  of  the  large  arteries  in  the 
limbs,  so  that  in  case  of  accident  you  could  stop  the  flow  of 
blood  i 

These  can  be  located  by  examining  the  cut  in  Physi- 
ology, page  104,  or  any  good  chart  of  the  circulation. 

15.  When  a  person  is  said  to  be  "good-hearted"  is  it  a 
physical  truth  ? 

The  expressions,  large-hearted,  good-hearted,  etc.,  are 
remains  of  the  old  idea  that  the  affections  are  located  in 
the  heart  rather  than  in  the  brain — the  seat  of  the  mind 
and  all  its  attributes. 

16.  Why  does  a  hot  foot-bath  often  relieve  the  headache1} 

(See  Physiology,  pages  127-8.) 

It  withdraws  blood  from  the  head,  and  so  relieves  the 
congested  state  of  that  organ. 


17°  ANSWERS  TO  PRACTICAL   QUESTIONS 

17.  Why  does  the  body  of  a  drowned  or  strangled  person 
turn  blue  ? 

The  blood  is  not  purified  in  the  lungs,  and  so  blue  or 
venous  blood  fills  the  vessels. 

1 8.  What  are  the  little  "  kernels  "  in  the  arm-pits  ? 

(See  Physiology,  page  123.) 

They  are  the  lymphatic  glands  which  sometimes  become 
swollen. 

19.  When  we  are  excessively  warm,  would  the  thermom- 
eter show  any  rise  of  temperature  in  the  body  ? 

(See  Physiology,  page  119,  note.) 

Probably  not.  In  health,  the  average  temperature  of 
the  body  does  not  vary  more  than  2°. 

20.  What  forces  besides  that  of  the  heart  aid  in  propelling 
the  blood  ? 

(See  Flint's  Physiology— The  Circulation  ;  Cutler's  Analytic  Anatomy^  etc.. 
page  166,  et  seq.) 

The  elasticity  of  the  arteries  and  the  veins,  the  force 
of  capillary  attraction  in  the  capillaries,  etc- 

2 1.  Why  can  the  pulse  be  felt  best  in  the  wrist  ? 

It  is,  in  general,  a  mere  matter  of  convenience.  We 
can  feel  it  not  only  in  the  radial  artery  at  the  wrist,  but 
in  the  carotid  of  the  neck,  the  temporal  of  the  forehead, 
the  popliteal  *  in  the  inner  side  of  the  knee,  etc. 

*  If  the  hollow  of  the  knee  of  one  leg  be  allowed  to  rust  upon  the  knee  ol 
the  other  one,  it  may  be  remarked  that  the  point  of  the  suscended  foot  moves 
visibly  up  and  down  at  each  beat  of  the  pulse. 


IN  HUMAN  PHYSIOLOGY.  *7X 

22.  Why  are  starving  people  exceedingly  sensitive  to  any 
jar? 

The  marrow  of  the  bones  is  absorbed,  and  hence  the 
shock  of  ajar  is  unbroken.  The  nervous  system  is  also 
weakened  by  the  general  prostration. 

23.  Why  will  friction,    an   application   of  horse-radish 
leaves,  or  a  blister  relieve  internal  congestion  1 

They  bring  the  blood  to  the  surface  of  the  body,  and 
so  relieve  the  internal  organ. 

24.  Why  are  students  very  liable  to  cold  feet  ? 

Because  the  tendency  of  the  blood  is  toward  the  head 
to  supply  the  waste  in  that  part  of  the  body. 

25.  Is  the  proverb  that  "blood  is  thicker  than  water" 
literally  true  ? 

(See  Draper's  Human  Physiology^  page  112.) 

The  specific  gravity  of  the  blood  varies  from  1.050  to 
1.059. 

26.  What  is  the  effect  upon  the  circulation  of  "holding 
the  breath  ?" 

The  blood  is  not  oxygenated,  the  products  of  waste 
accumulate  in  the  system,  the  circulation  is  impeded,  the 
blood-vessels  become  distended  and  are  liable  to  burst, 
while  all  the  delicate  organs,  especially  the  brain,  are 
oppressed  by  congestion. 

27.  Which  side  of  the  heart  is  the  stronger  ? 

The  left,  which  drives  the  blood  to  the  extremities. 


I?2  AtfSWEXS  TO  PRACTICAL   QUESTIONS 

28.  How  is  the  heart  itself  nourished  ? 

The  coronary  arteries  springing  from  the  aorta  just 
after  its  origin,  carry  blood  to  the  muscular  walls  of  the 
heart :  the  venous  blood  comes  back  through  the  coronary 
veins,  and  empties  directly  into  the  right  auricle. 

29.  Does  any  venous  blood  reach  the  heart  without  com- 
•Ing  through  the  vena  cavcz  ? 

(See  Question  28.) 

155. — i.  How  do  clothing  and  shelter  economize  food  ? 

The  force  which  would  be  converted  into  heat  to  pre- 
serve the  temperature  of  the  body,  is  saved.  The  food 
needed  to  supply  this  amount  of  force  may  be  reserved 
or  changed  into  flesh,  or  into  other  forms  of  force. 

2.  Is  it  well  to  take  a  long  walk  before  breakfast  ? 

(See  Physiology,  page  53.) 

A  vigorous  person  in  good  health  and  in  a  healthy 
region  may  do  so,  but  one  in  ill  health,  or  a  malarious 
district,  needs  to  be  braced  with  food  before  taking  any 
except  very  light  exercise. 

3.  Why  is  warm  food  easier  to  digest  than  cold? 

Heat  favors  the  chemical  change  whereby  the  food  is 
prepared  for  assimilation. 

4.  Why  is  salt  beef  less  nutritious  than  fresh  ? 

(See  Physiology,  page  155,  note.) 

The  salts  and  juices  of  the  meat  are  extracted  by  the 
brine. 


IN  HUMAN  PHYSIO L OGY.  173 

5.  What  should  be  the  food  of  a  man  recovering  from  a 
fever? 

It  should  be  that  which  is  nutritious,  easily  digested, 
and  not  over-stimulating.  Beef-tea  or  essence*  is  gener- 
ally commended.  As  soon  as  the  patient  will  bear  it, 
beefsteak,  tender,  broiled,  and  not  over-done,  is  most 
beneficial. 

6.  Is  a  cup  of  black  coffee  a  healthy  close  to  a  hearty 
dinner  ? 

The  tannic  acid  contained  in  tea  and  coffee  (see  Chem- 
istry, pp.  211,  215)  is  neutralized  by  the  milk  generally 
used  with  these  beverages.  In  cafe  noir,  black  or 
clear  coffee,  the  tannic  acid  acts  unfavorably  on  the 
mucous  membrane  lining  the  stomach.  Besides,  the 
coffee,  like  a  dessert,  is  superfluous,  the  appetite  being 
already  satisfied.  It  therefore,  both  actively  and  nega- 
tively, tends  to  delay  the  digestion  of  the  meal.  The 
glass  of  wine  sometimes  taken  to  aid  digestion  merely 
deadens  the  sensibility  of  the  stomach,  so  that  the  food  is 
hurried,  half-digested,  out  into  the  intestines.! 

7.  Should  ice-water  be  used  at  a  meal  ? 

Only  a  person  in  robust  health  can  endure  the  shock 

*  Dr.  Martindale  gives  the  following  recipe  for  making  this  essence : 
Cut  a  quantity  of  lean  beef  into  small  pieces,  put  it  into  a  strong  bottle, 
without  water,  cork  it  loosely  so  that  the  steam  can  escape,  and  immerse  the 
bottle  to  its  neck  in  a  vessel  of  cold  water.  Place  on  the  fire  and  boil  for  two 
hours  ;  then  pour  off  the  essence. 

t  Mix  some  bread  and  meat  with  gastric  juice  ;  place  them  in  a  phial,  and 
keep  that  phial  in  a  sand-bath  at  the  slow  heat  of  98  degrees,  occasionally 
shaking  briskly  the  contents  to  imitate  the  motion  of  the  stomach  ;  you  will 
find,  after  six  or  eight  hours,  the  whole  contents  blended  into  one  pultaceous 
mass.  If  to  another  phial  of  food  and  gastric  juice,  treated  in  the  same  way, 
you  add  a  glass  of  pale  ale  or  a  quantity  of  alcohol,  at  the  end  of  seven  or  eight 
hours,  or  even  some  days,  the  food  is  scarcely  acted  upon  at  all. 


174  ANSWERS  TO  PRACTICAL   QUESTIONS 

of  drinking  ice-water  at  a  meal.  Indeed,  drinking  of  ice- 
water  under  any  circumstances  is  dangerous  and  hurtful. 
If  used  at  all,  it  should  be  carefully  and  slowly  sipped,  a 
little  at  a  time. 

8.  Why  is  strong  tea  or  coffee  injurious  ? 

The  tannic  acid  acts  unfavorably  on  the  coatings  of 
the  stomach.*  The  nervous  system  is  over-stimulated, 
and,  when  the  reaction  occurs,  becomes  correspondingly 
depressed  and  weakened.  The  constant  decay  of  the 
body,  so  essential  to  its  highest  activity,  is  greatly  re- 
tarded. Wakefulness  is  often  induced,  and  thus  the 
organs  are  deprived  of  that  rest  which  is  absolutely  es- 
sential. 

9.  Should  food  or  drink  be  taken  hot  ? 

The  pepsine  of  the  gastric  juice,  in  order  to  produce  its 
effect,  must  have  a  moderately  warm  temperature,  neither 
too  hot  nor  too  cold.  The  gastric  juice  will  not  act  upon 
the  food  when  near  the  freezing  point  of  water,  neither 
will  it  have,  any  effect  if  raised  to  the  neighborhood  of  a 
boiling  temperature.  It  must  be  intermediate  between 
the  two;  and  its  greatest  activity  is  about  100  degrees 
Fahrenheit,  which  is  exactly  the  temperature  of  the  in- 
terior of  the  living  stomach. — DALTON'S  Physiology,  p.  103. 

10.  Are  fruit-cakes,  rich  pastry,  and  puddings  healthful? 

(See  BLACK'S  Ten  Laws  of  Health,  p.  83,  et  seq.) 

They  are  too  concentrated.  They  are  not  easily  pene- 
trated by  the  juices  of  the  system,  and  hence  are  not 
quickly  digested.  They  stimulate  the  appetite,  and  so 

*  Tea  contains  from  14  to  16  per  cent,  of  this  astringent  substance,  and 
coffee  not  over  6  per  cent.— YOUMANS. 


IN  HUMAN  PHTSIOL  OOT.  175 

lead  to  gluttony.  They  supply  the  system  with  an  over- 
abundance of  nutrition,  for  which  the  blood  has  no  use, 
and  so  lead  to  biliousness  and  other  diseases  of  the  blood 
and  digestive  organs. 

1 1.  Why  are  warm  biscuit  and  bread  hard  of  digestion  ? 

They  form  a  pasty  mass,,  which  the  juices  of  the  diges- 
tive organs  penetrate  very  slowly. 

12.  Should  any  stimulants  be  used  in  youth  ? 

No.  The  system  is  then  vigorous,  and  all  its*  functions 
promptly  performed.  If  stimulants  are  ever  used,  it 
should  be  when  the  body  needs  forcing,  as  when  recover- 
ing from  disease,  or  languid  with  the  decay  of  the  natural 
powers  in  old  age. 

13.  Why  should  bread  be  made  spongy  ? 

(See  Question  n.) 

14.  Which  should  remain  longer  in  the  mouth,  bread  or 
meat? 

Bread,  since  the  pepsin  is  essential  to  the  conversion 
of  starch  into  sugar  ? 

15.  Why  should  cold  water  be  used  in  making  soup,  and 
hot  in  boiling  meat  ? 

In  the  former  case,  we  desire  to  extract  the  juices  of 
the  meat ;  in  the  latter,  to  retain  this  by  quickly  coagu- 
lating the  albumen  on  the  surface  of  the  meat 

1 6.  Name  the  injurious  effects  of  over-eating. 

(See  Physiology,  page  151.) 

17.  Why  do  not  buckwheat  cakes,  with  syrup  and  butter, 
taste  as  well  in  July  as  in  January  ? 

In  the  winter,  the  system  craves  highly  carbonaceous 


I76  ANSWERS  TO  PRACTICAL  QUESTIONS 

food ;  in  the  summer,  it  relishes  cooling,  acid  drinks,  and 
an  unstimulating  diet. 

1 8.    Why  is  a  late  supper,  injurious  ? 

The  system  is  wearied  with  the  clay's  labor,  and  the 
stomach  is  unfitted  to  undertake  the  task  of  digesting  a 
meal  as  much  as  the  body  is  to  begin  a  new  day's  task 
unrefreshed  by  sleep.* 

*  "  Being  allowed  for  once  to  speak,  I  would  take  the  opportunity  to  set 
forth  how  ill,  in  all  respects,  we  stomachs  are  used.  From  the  beginning  to 
the  end  of  life,  we  are  either  afflicted  with  too  little  or  too  much,  or  not  the 
right  thing,  or  things  which  are  horribly  disagreeable  to  us  ;  or  are  otherwise 
thrown  into  a  state  of  discomfort.  I  do  not  think  it  proper  to  take  up  a 
moment  in  bewailing  the  Too  Little,  for  that  is  an  evil  which  is  never  the 
fault  of  our  masters,  but  rather  the  result  of  their  misfortunes  ;  and,  indeed, 
we  would  sometimes  feel  as  if  it  were  a  relief  from  other  kinds  of  distress  if 
we  were  put  upon  short  allowance  for  a  few  days.  But  we  conceive  our- 
selves to  have  matter  for  serious  complaint  against  mankind  in  respect  of  the 
Too  Much,  which  is  always  an  evil  voluntarily  incurred.  What  a  pity  that  in 
the  progress  of  discovery  we  cannot  establish  some  means  of  a  good  under- 
standing between  mankind  and  their  stomachs  ;  for  really  the  effects  of  their 
non-acquaintance  are  most  vexatious.  Human  beings  seem  to  be,  to  this  day, 
completely  in  the  dark  as  to  what  they  ought  to  take  at  any  time,  and  err 
almost  as  often  from  ignorance  as  from  depraved  appetite.  Sometimes,  for 
instance,  when  we  of  tfie  inner  house  are  rather  weakly,  they  will  send  us 
down  an  article  that  we  could  deal  with  when  only  in  a  state  of  robust  health. 
Sometimes,  when  we  would  require  a  mild  vegetable  diet,  they  will  persist  in 
the  most  stimulating  and  irritating  of  viands. 

"  What  sputtering  we  poor  stomachs  have  when  mistakes  of  that  kind  occur ! 
What  remarks  we  indulge  in  regarding  our  masters  !  "  What's  this,  now  ? " 
will  one  of  us  say ;  "  ah,  detestable  stuff !  What  a  ridiculous  fellow  that  man 
is  !  Will  he  never  learn  ?  Just  the  very  thing  I  did  not  want  If  he  would 
only  send  down  a  bowl  of  fresh  leek  soup  or  barley  broth,  there  would  be 
some  sense  in  it :"  and  so  on.  If  we  had  only  been  allowed  to  give  the 
slightest  hint  now  and  then,  like  faithful  servants  as  we  are,  from  how  many 
miseries  might  we  have  saved  both  our  masters  and  ourselves  ! 

"  I  have  been  a  stomach  for  about  forty  years,  during  all  of  which  time  I  have 
endeavored  to  do  my  duty  faithfully  and  punctually.  My  master,  however, 
is  so  reckless,  that  I  would  defy  any  stomach  of  ordinary  ability  and  capacity 
to  get  along  pleasantly  with  him.  The  fact  is,  like  almost  all  other  men,  he, 
in  his  eating  and  drinking,  considers  his  own  pleasure  only,  and  never  once 
reflects  on  the  poor  wretch  who  has  to  be  responsible  for  the  disposal  of 
everything  down  stairs.  Scarcely  on  any  day  does  he  fail  to  exceed  the  strict 


IN  HUMAN  PHYSIOLOGY.  177 

19.    What  makes  a  man  "  bilious  ?  " 

(See  Hall's  Health  by  Good  Living,  p.  in,  et  seq.) 

The  liver  strains  the  bile  out  of  the  blood.  This  waste 
matter  is  not  withdrawn  when  the  liver  is  inactive,  and 
hence  the  face  and  eyes  become  yellow — the  cclor  of  bile, 
and  the  functions  all  become  torpid. 

rule  of  temperance  ;  nay,  there  is  scarcely  a  single  meal  which  is  altogether 
what  it  ought  to  be.  My  life  is  therefore  one  of  continual  worry  and  fret ;  I 
am  never  allowed  to  rest  from  morning  till  night,  and  have  not  a  moment  in 
the  four-and-twenty  hours  that  I  can  safely  call  my  own.  My  greatest  trial 
takes  place  in  the  evening,  when  my  master  has  dined.  If  you  only  saw  what 
a  mess  this  said  dinner  is — soup,  fish,  flesh,  fowl,  ham,  rice,  potatoes,  table- 
beer,  sherry,  tart,  pudding,  cheese,  bread,  all  mixed  up  together.  I  am  ac- 
customed to  the  thing,  so  don't  feel  much  shocked  ;  but  my  master  himself 
would  faint  at  the  sight.  The  slave  of  duty  in  all  circumstances,  I  call  in  my 
friend  Gastric  Juice,  and  we  set  to  work  with  as  much  good-will  as  if  we  had 
the  most  agreeable  task  in  the  world  before  us.  But,  unluckily,  my  master 
has  an  impression  very  firmly  fixed  upon  him  that  our  business  is  apt  to  be 
vastly  promoted  by  an  hour  or  two's  drinking ;  so  he  continues  at  table 
among  his  friends,  and  pours  down  some  bottle  and  a  half  of  wine,  perhaps  of 
various  sorts,  that  bothers  Gastric  Juice  and  me  to  a  degree  which  no  one  can 
have  any  idea  of.  In  fact,  this  said  wine  undoes  our  work  almost  as  fast  as 
we  do  it,  besides  blinding  and  poisoning  us  poor  servants  into  the  bargain. 
On  many  occasions  I  am  obliged  to  give  up  my  task  for  the  time  altogether  ; 
for  while  this  vinous  shower  is  going  on  I  would  defy  the  most  vigorous 
stomach  in  the  world  to  make  any  advance  in  its  business  worth  speaking  of. 
Sometimes  things  go  to  a  mu  ch  greater  length  than  at  others  ;  and  my  master 
will  paralyze  us  in  this  manner  for  hours,  not  always,  indeed,  with  wine,  but 
occasionally  with  punch,  one  ingredient  of  which — the  lemon — is  particularly 
odious  to  us.  All  this  time  I  can  hear  him  jollifying  away  at  a  great  rate, 
drinking  healths  to  his  neighbors,  and  ruining  his  own. 

"  I  am  a  lover  of  early  hours,  as  are  my  brethren  generally.  To  this  we  are 
very  much  disposed  by  the  extremely  hard  work  which  we  usually  undergo 
during  the  day.  About  ten  o'clock,  having,  perhaps,  at  that  time  got  all  our 
labors  past,  and  feeling  fatigued  and  exhausted,  we  like  to  sink  into  repose, 
not  to  be  again  disturbed  till  next  morning  at  breakfast-time.  Well,  how  it 
may  be  with  others  I  can't  tell ;  but  so  it  is,  that  my  master  never  scruples  to 
rouse  me  up  from  my  first  sleep,  and  give  me  charge  of  an  entirely  new  meal, 
after  I  thought  I  was  to  be  my  own  master  for  the  night.  This  is  a  hardship 
of  the  most  grievous  kind.  Only  imagine  me,  after  having  gathered  in  my 
coal,  drawn  on  my  night-cap,  and  gone  to  bed,  called  up  and  made  to  take 
charge  of  a  quantity  of  stuff  which  I  know  I  shall  not  be  able  to  get  off  my 
hands  all  night !  Such,  O  mankind,  are  the  woes  which  befall  our  tribe  i* 
8 


178  ANSWERS  TO  PRACTICAL   QUESTIONS 

20.  What  is  the  best  remedy  ? 

Diet  to  give  the  organs  rest,  and  active  exercise  to 
arouse  the  secretions  and  the  circulation. 

2 1.  What  is  the  practical  use  of  hunger  ? 

To  prompt  us  to  furnish  the  body  with  sufficient  food. 

22.  How  can  jugglers   drink    when   standing  on   their 
heads  ? 

Because  water  does  not  fall  into  the  stomach  by  its 
own  weight,  but  is  conveyed  thither  from  the  mouth  by 
the  contraction  of  the  muscular  bands  of  the  oesophagus. 

consequence  of  your  occasionally  yielding  to  the  temptations  of  "  a  little 
supper."  I  see  turkey  and  tongue  in  grief  and  terror.  Macaroni  fills  me 
with  frantic  alarm.  I  behold  jelly  and  trifle  follow  in  mute  despair.  O  that 
I  had  the  power  of  standing  beside  my  master,  and  holding  his  unreflecting 
hand,  as  he  thus  prepares  for  my  torment  and  his  own  !  Here,  too,  the  old 
mistaken  notion  about  the  need  of  something  stimulating  besets  him,  and 
down  comes  a  deluge  of  hot  spirits  and  water,  that  causes  me  to  writhe  in 
agony,  and  almost  sends  Gastric  Juice  off  in  the  sulks  to  bed.  Nor  does  the 
infatuated  man  rest  here.  If  the  company  be  agreeable,  one  glass  follows 
another,  while  I  am  kept  standing,  as  it  were,  with  my  sleeves  tucked  up, 
ready  to  begin,  but  unable  to  perform  a  single  stroke  of  work. 

"  I  feel  that  the  strength  which  I  ought  to  have  at  my  present  time  of  life  has 
passed  from  me.  I  am  getting  weak,  and  peevish,  and  evil-disposed.  A  com- 
paratively small  trouble  sits  long  and  sore  upon  me.  Bile,  from  being  my 
servant,  is  becoming  my  master  ;  and  a  bad  one  he  makes,  as  all  good  ser- 
vants ever  do.  I  see  nothing  before  me  but  a  premature  old  age  of  pains  and 
groans,  and  gripes  and  grumblings,  which  will,  of  course,  not  last  over  long  ; 
and  thus  I  shall  be  cut  short  in  my  career,  when  I  should  have  been  enjoying 
life's  tranquil  evening,  without  a  single  vexation  of  any  kind  to  trouble  me. 
Were  I  of  a  revengeful  temper,  it  might  be  a  consolation  to  think  that  my 
master — the  cause  of  all  my  woes — must  suffer  and  sink  with  me  ;  but  I  don't 
see  how  this  can  mend  my  own  case  ;  and,  from  old  acquaintance,  I  am  rather 
disposed  to  feel  sorry  for  him,  as  one  who  has  been  more  ignorant  and  im- 
prudent than  ill-meaning.  In  the  same  spirit  let  rne  hope  that  this  true  and 
unaffected  account  of  my  case  may  prove  a  warning  to  other  persons  how 
they  use  their  stomachs ;  for,  they  may  depend  upon  it,  whatever  injustice 
they  do  to  us,  in  their  days  of  health  and  pride,  will  be  repaid  to  themselves  in 
the  long-run — our  friend  Madame  Nature  being  a  remarkably  accurate  ac- 
countant, who  makes  no  allowance  for  ignorance  or  mistakes."— CHAMBERS' 
Memoir  of  a  Stomach. 


IN  HUMAN  PHYSIOLOGY.  179 

23.  Why  do  we  relish  butter  on  bread  ? 

Butter  supplies  the  carbonaceous  element  in  which 
bread  is  lacking. 

24.  Is  chewing  tobacco  more  injurious  than  smoking? 

(See  Cutler's  Physiology,  pages  242-4.) 

It  is  not  only  more  filthy,  but  also  more  detrimental  to 
the  health,  as  thereby  a  greater  proportion  of  the  poison- 
ous alkaloids  of  the  tobacco  is  carried  into  the  system. 
Among  the  too  frequent  evil  effects  of  this  powerful 
narcotic  are  an  impaired  nutrition,  a  poisoned  circulation, 
a  stupefied  mind  and  conscience — evils  which  end  not  with 
the  parent  but  are  transmitted  many-fold  to  the  child. 

25.  Why  should  ham  and  sausage  be  thoroughly  cooked  ? 

The  trichina,  which  frequents  pork,  is  only  destroyed 
at  a  high  temperature. 

26.  Why  do  we  wish  butter  on  fish,  eggs  with  tapioca,  oil 
on  salad,  and  milk  with  rice  ? 

To  supply  the  elements  of  food  lacking  in  the  compo- 
sition of  fish,  tapioca,  etc. 

27.  Explain  the  relation  of  food  to  exercise. 

Their  relation  is  exceedingly  intimate.  If  we  eat  much 
we  should  take  more  exercise,  and  if,  on  the  contrary,  we 
labor  more,  we  desire  additional  food.  Violent  exercise, 
directly  after  a  hearty  meal,  is  injurious  ;  but  a  gentle, 
quiet  half-hour's  saunter  will  greatly  benefit  the  digestion. 

28.  How  do  you  explain  the  difference  in  the  manner  of 
eating  between  carnivorous  and  herbivorous  animals  ? 

Meat  requires  less  saliva  to  aid  in  its  digestion,  and 


l8o  ANSWERS  TO  PRACTICAL   QUESTIONS 

henc  i  it  is  mainly  digested  in  the  stomach  ;  while  vege- 
table food  needs  to  be  thoroughly  masticated  and  incor- 
porated with  the  salivary  mucus. 

29.  Why  is   a   child 's  face  plump   and  an  old  marts 
wrinkled  ? 

In  the  child  the  processes  of  nutrition  are  more  active 
than  those  of  waste.  The  reverse  is  the  case  in  old  age. 

30.  Show  how  life  depends  on  repair  and  waste. 

(See  Chemistry,  page  34,  et  sey.  ;  and  Physiology,  page  120.) 

31.  What  is  the  difference  between  the  decay  of  the  teeth 
and  the  constant  decay  of  the  body  ? 

The  particles  of  the  teeth  lost  by  decay  are  not 
renewed,  while  in  the  body  they  are  replaced  as  fast  as 
worn  out. 

32.  Should  biscuit  and  cake  containing  yellow  spots  of 
soda  be  eaten  ? 

Certainly  not.  The  alkali  neutralizes  the  acids  of  the 
alimentary  juices,  and  thus  impairs  their  functions,  while 
it  corrodes  and  irritates  the  delicate  mucous  lining  of 
the  digestive  organs. 

33.  Tell  how  the  body  is  composed  of  organs,  organs  are 
made  up  of  tissues,  and  tissues  of  cells. 

(See  Physiology,  page  154,  note.) 

34.  Why  do  we  not  need  to  drink  three  pints  of  water 
per  day  ? 

(See  Physiology,  page  133.) 

The  amount  of  water  one  needs  depends  upon  the 


IN  HUMAN  PHTSIOL OGT.  I  8 1 

character  of  his  food,  the  nature  of  his  labor,  and  the 
activity  of  the  three  eliminating  organs — the  skin,  the  kid- 
neys, and  the  lungs.  One  perspiring  freely,  or  eating  dry 
food,  needs  more  drink  than  one  whose  skin  is  inactive, 
or  whose  food  consists,  in  part,  of  soups  or  watery  vege- 
tables. 

35.  Why,  during  a  pestilence,  are  those  who  use  liquors 
as  a  beverage  the  first,  and  often  the  only  victims  ? 

The  nervous  system  becomes  impaired,  the  digestion 
weakened,  and  the  blood  impoverished :  hence,  the  func- 
tions of  the  body  being  disturbed,  its  ability  to  resist 
disease  is  greatly  impaired.  It  is  said  that  the  alcohol 
hardens  the  albuminous  matter  of  the  brain  and  the  mem- 
branous lining  of  the  lungs,  and  hence  clogs  the  action 
of  these  organs. 

36.  What  two  secretions  seem  to  have  the  same  general 
use? 

The  saliva  and  the  pancreatic  juice  both  change  starch 
into  sugar.  They  have  other  important  uses,  however,  in 
the  process  of  digestion.  The  former  softens  the  food 
and  aids  in  the  work  of  mastication,  while  the  latter 

emulsifies  the  fats. 

37.  How  may  the  digestive  organs  be  strengthened? 

The  digestive  organs,  like  the  other  organs,  are  strength- 
ened by  judicious  labor.  The  stomach  is  a  muscle,  and 
like  muscle,  generally  grows  strong  by  use  and  weak  by 
disuse.  The  same  laws  should  govern  one  in  his  daily 
exercise  of  every  organ — brain,  hand,  and  stomach. 


1 82  ANSWERS  TO  PRACTICAL   QUESTIONS 

175. — i.  Why  is  the  pain  of  incipient  hip-disease  fre- 
quently felt  in  the  knee  ? 

The  sensation  of  pain  is  located  by  the  mind,  at  the 
part  of  the  body  where  the  injured  nerve  takes  it  rise. 

2.  Why  does  a  child  require  more  sleep  than  an  aged 
person  ? 

The  processes  of  nutrition  are  going  on  rapidly,  and, 
in  youth,  much  rest  is  required  to  repair  the  losses  of 
each  day ;  in  age,  waste  predominates,  and  the  repairs 
made  are  of  a  temporary  character.  The  building  is  soon 
to  be  torn  down,  and  little  effort  is  taken  to  beautify  or 
strengthen  that  which  is  to  be  used  for  so  short  a  time. 

3.  When  you  put  your  finger  in  the  palm  of  a  sleeping 
child,  why  will  he  grasp  it  ? 

The  unconscious  action  of  the  near  nervous  centers 
produces  a  contraction  of  the  muscles. 

4.  How  may  we  strengthen  the  brain  ? 

By  judicious,  habitual,  but  not  exhaustive  employment. 
The  life  of  the  brain  is  in  change.  Monotony  is  stagna- 
tion, and  stagnation  is  decay. 

5.  What  is  the  object  of  pain  ? 

Pain  is  monitory  in  its  character.  It  guards  against 
danger  and  warns  us  of  the  presence  of  dfrease,  z.  e.,  the 
want  of  ease.  Were  it  not  for  this,  we  should  lose  the 
use  of  the  more  delicate  organs.  A  child  might  gaze  at 
the  sun  until  its  eyesight  was  ruined.  The  author  knew 
of  a  man  who  had  lost  the  sense  of  feeling  in  one  leg 


IN  HUMAN  PHYSIOLOGY.  183 

because  of  the  sensory  nerve  being  severed.  He  was 
constantly  bruising  and  burning  that  limb  until  he  ruined 
it  entirely. 

6.  Why  will  a  blow  on  the  stomach  sometimes  stop  the 
heart? 

By  sympathy.  The  pneumogastric  or  tenth  pair  of 
nerves  supply  the  stomach  and  the  heart. 

7.  How  long  will  it  take  for  the  brain  of  a  man  six  feet 
high  to  receive  news  of  an  injury  to  his  foot,  and  to  reply  ? 

The  nervous  force  has  been  estimated  to  travel  at  the 
rate  of  100  feet  per  second,  although  authorities  vary 
much.  Taking  this  figure,  it  would  require  about  one- 
eighth  of  a  second.* 

8.  How  can  we  grow  beautiful  ? 

If  one  is  penurious,  selfish,  or  hard-hearted,  his  face 
will  betray  the  fact  to  every  passer  by.  Purity  of  thought 
and  nobleness  of  soul,  the  simple  habit  of  cherishing  high 
and  generous  purposes,  refine  and  spiritualize  the  coun- 
tenance, making,  at  last,  the  homeliest  features  to  glow 
with  a  beauty  that  will  be  a  true  "joy  forever." 

9.  Why  do  intestinal  worms  ever  affect  a  child's  sight  ? 
Through  the  action  of  the  sympathetic  system  of  nerves. 

10.  Is  there  any  indication  of  character  in  physiognomy  1 

(See  Question  8  ;  also  Physiology,  page  171.) 

*  A  bare-footed  boy  steps  on  a  thorn.  If  he  had  to  wait  for  news  of  the 
injury  to  be  sent  to  his  brain,  and  an  order  to  be  telegraphed  back  to  remove 
the  foot,  much  time  would  be  lost.  As  it  is,  with  the  first  prick,  the  nearer 
nerve-centers  act  and  order  the  foot  off  almost  before  the  brain  has  heard  o* 
the  accident. 


184.  ANSWERS  TO  I'RACTICAL   QUESTIONS 

1 1.  When  one's  finger  is  burned,  where  is  the  ache  ? 

All  pain  is  in  the  brain.     It  is  located,  however,  by  the 
mind,  at  the  place  of  the  injury. 

12.  Is  a  parlor  generaHy  a  healthy  room  ? 

No.  It  is  generally  ill-ventilated,  and,  to  preserve  the 
furniture,  kept  dark,  and  hence  damp. 

13.  Why  can  an  idle  scholar  read  his  lesson  and  at  the 
same  time  count  the  marbles  in  his  pocket  ? 

The  duality  of  the  brain  may,  perhaps,  account  for  this. 

(See  Physiology,  page  162,  note.) 

14.  In  amputating  a  limb,  what  part,  when  divided,  will 
cause  the  keenest  pain  ? 

When  a  surgical  operation  is  performed,  the  most  pain- 
ful part  of  it  is  the  incision  through  the  skin  ;  the  muscles, 
cartilage,  and  bone  being  comparatively  without  sensa- 
tion. Hence,  if  we  could  benumb  the  surface,  certain  of 
the  lesser  operations  might  be  undergone  without  great 
inconvenience.  This  is,  in  fact,  very  successfully  accom- 
plished by  means  of  the  cold  produced  by  throwing  a 
spray  of  ether,  or  of  some  other  rapidly  evaporating  liquid, 
upon  the  part  to  be  cut. 

1 5.  What  is  the  effect  of  bad  air  on  nervous  people  ? 

The  nerves  connect  all  the  organs  of  the  body.  They 
are  therefore  especially  sensitive  to  a  derangement  in  the 
function  of  any  organ.  Bad  air  causes  impure  blood,  de- 
ranged nutrition,  and  hence  a  disturbance  of  the  entire 
economy. 


IN  HUMAN  PHYSIOLOGY.  185 

1 6.  Is  there  any  truth  in  the  proverb  that  "he  who  sleeps •, 
dines  V 

The  proverb  expresses  the  fact  that  the  nourishment  of 
the  brain  and  other  parts  goes  on  actively  during  sleep, 
they  being  controlled  by  the  sympathetic  nerves 

17.  What  does  a  high,  wide  forehead  indicate  ? 

It  suggests  a  large  brain  and  a  high  intellectual 
power. 

1 8.  How  does  indigestion  frequently  cause  a  headache  1 
Through  the  action  of  the  sympathetic  system. 

19.  What  is  the  cause  of  the  f oof  s  being  "  asleep  ?  " 

(See  Physiology,  page  176,  note.) 

20.  When  an  injury  to  the  nose  has  been  remedied  by 
transplanting  skin  from  the  forehead,  why  is  a  touch  to  the 
former  felt  in  the  latter  ? 

The  mind  refers  the  sensation  to  the  place  where  the 
nerve  naturally  had  its  origin — /'.  e.,  the  part  over  which 
its  tiny  fibres  were  originally  distributed. 

21.  Are  closely-curtained  windows  healthy  ? 
No.  They  keep  out  the  sun  and  the  fresh  air. 

22.  Why,  in  falling  from  a  height,  do  the  limbs  instinc- 
tively take  a  position  to  defend  the  important  organs  ? 

The  reflex  action  of  the  spinal  cord  moves  the  limbs 
into  a  position  of  defence,  the  brain  having  no  time  to 
act. 


1 86  ANSWERS  TO  PRACTICAL   QUESTIONS 

23.  What  causes  the  pylorus  to  open  and  close  at  the  right 
time  ? 

The  reflex  action  of  the  nerves  which  preside  over  that 
organ.  In  a  similar  way,  a  tickling  in  the  throat  excites 
coughing. 

24.  Why  is  pleasant  exercise  most  beneficial'} 

A  chief  condition  of  keeping  the  brain  healthy  is  to 
keep  the  unconscious  nervous  functions  in  full  vigor,  and 
in  natural  alternations  of  activity  and  repose.  Thus  it  is 
that  (besides  its  effect  in  increasing  the  breathing  and  the 
general  vigor  of  the  vital  processes)  muscular  exercise 
has  so  manifest  a  beneficial  influence  on  a  depressed  or 
irritable  state  of  mind.  The  bodily  movement,  by  afford- 
ing an  outlet  to  the  activity  of  the  spinal  cord,  withdraws 
a  source  of  irritation  from  the  brain ;  or  it  may  relieve  ex- 
citement of  that  organ  by  carrying  off  its  energy  into  a 
safe  channel. — HINTON. 

25.  Why  does  grief  cause  one  to  lose  his  appetite  ? 
Through  the  action  of  the  sympathetic  system. 

26.  Why  should  we  never  study  directly  after  dinner  ?  . 

The  blood  then  sets  toward  the  stomach,  and  the  whole 
strength  of  the  system  is  needed  to  properly  digest  the 
food. 

27.  What  produces    the   peristaltic    movement    of  the 
stomach  ? 

The  presence  of  the  food  which,  through  the  sympa- 
thetic system,  acting  involuntarily,  sets  in  motion  the 
complicated  apparatus  of  digestion. 


IN  HUMAN  PHYSIOL OGT.  187 

28.  Why  is  a  healthy  child  so  restless  and  full  of  mis- 
chief? 

Nature  prompts  it  to  exercise  all  the  muscles  in  its  body 
in  order  to  their  proper  development. 

29.  Why  is  a  slight  blow  on  the  back  of  a  rabbit's  neck 
fatal? 

.    The  medulla  oblongata   is    not   defended   with   thick 
muscles  as  in  man. 

30.  Why  can  one  walk  and  carry  on  a  conversation  at 
the  same  time  ? 

(See  Question  13,  page  176.) 

3 1.  What  are  the  dangers  of  over-study  ? 

(See  Hinton's  Health  and  its  Conditions,  page  IQS,  et  seq.,   and  Cutler's 
Analytical  Anatomy,  page  248.) 

Exhaustive  mental  labor  overstrains  the  delicate  nerve- 
cells  of  the  brain,  and  the  condition  of  the  blood-vessels 
of  the  entire  body,  especially  of  the  vital  organs,  is  regu- 
lated, moment  by  moment,  by  its  changing  moods.  Even 
the  supply  furnished  the  brain  is  subject  to  the  same 
influence.  Hence  results  deranged  nutrition,  impaired 
circulation,  and  weakened  brain  and  body.  Whenever 
we  consume  vital  energy  faster  than  it  can  be  replaced, 
we  encroach  upon  the  capital,  and  thus  cause  an  irrepar- 
able injury. 

32.  What  is  the  influence  of  idleness  upon  the  brain  ? 

If  we  would  have  healthy  bodies  we  must  have  active 
brains,  that  the  streams  of  force  may  flow  into  every 
organ  from  a  full,  fresh,  energizing  source.  "  The  perfect 


1 88  ANSWERS  TO  PRACTICAL  QUESTIONS 

health  of  a  man  is  not  that  of  an  ox  or  a  horse."  The 
proper  exercise  of  the  brain  is  an  essential  element  of 
real  life. 

33.  State  the  close  relation  which  exists  between  physical 
and  mental  health  and  disease. 

"  A  partial  cultivation  of  the  mental  faculties  is  incom- 
patible not  only  with  the  highest  order  of  thought,  but 
with  the  highest  degree  of  health  and  efficiency.  The 
result  of  professional  experience  fairly  warrants  the 
statement  that  in  persons  of  a  high  grade  of  intellec- 
tual endowment  and  cultivation,  other  things  being  equal, 
the  force  of  moral  shocks  is  more  easily  broken,  tedious 
and  harassing  exercise  of  particular  powers  more  safely 
borne,  than  in  those  of  an  opposite  description,  and  dis- 
ease, when  it  comes,  is  more  readily  controlled  and  cured. 
The  kind  of  management  which  consists  in  awakening  a 
new  order  of  emotion,  in  exciting  new  trains  of  thought, 
in  turning  attention  to  some  new  matter  of  study  or 
speculation,  must  be  far  less  efficacious,  because  less 
applicable,  in  one  whose  mind  has  always  had  a  limited 
range  than  in  one  of  larger  resources  and  capacities.  In 
endeavoring  to  restore  the  disordered  mind  of  the  clod- 
hopper who  has  scarcely  an  idea  beyond  that  of  his 
manual  employment,  the  great  difficulty  is  to  find  some 
available  point  from  which  conservative  influences  may 
be  projected.  He  dislikes  reading,  he  never  learned 
amusements,  he  feels  no  interest  in  the  affairs  of  the 
world  ;  and  unless  the  circumstances  allow  of  some  kind 
of  bodily  labor,  his  mind  must  remain  in  a  state  of  soli- 
tary isolation,  brooding  over  its  morbid  fancies,  and 
utterly  incompetent  to  initiate  any  recuperative  move 
ment" — Dr.  RAY. 


IN  HUMAN  PH  T8IOL  OGY.  189 

34.  In  what  consists  the  value  of  the  power  of  habit  ? 

It  saves  the  "  wear  and  tear  "  of  our  principles.  We 
can  perform  an  act  a  few  times,  though  with  difficulty, 
and  then  ever  after  it  becomes  a  habit.  We  resist  evil 
once,  and  thenceforth  it  is  easier.  We  can  become 
accustomed  to  do  good,  so  that  the  chances  will  all  be 
in  favor  of  our  well-being  in  any  emergency.  By  as  much 
'  as  the  power  of  habit  is  thus  pregnant  with  good,  by  so 
much  is  it  susceptible  of  terrible  evil. 

35.  How  many  pairs  of  nerves  supply  the  eye  ? 

(See  Physiology^  page  167.) 

Three  ;  the  motores  oculi. 

36.  Describe  the  reflex  actions  in  reading  aloud. 

The  body  is  kept  erect,  the  hand  holds  the  book,  the 
eyes  are  directed  to  the  page,  the  vocal  organs  pronounce 
the  words,  the  features  express  the  sentiments,  and  the 
other  hand  makes  corresponding  gestures — yet  all  the 
time  the  mind  is  intent  only  upon  the  thought  conveyed. 

37.  Under  what  circumstances  does  paralysis  occur'} 

When  the  nerve  leading  to  any  part  of  the  body  is 
injured  or  fails  to  keep  up  communications  between  that 
portion  and  the  mind. 

38.  If  the  eyelids  of  a  profound  sleeper  were  raised,  and  a 
candle  bt  ought  near,  would  the  iris  contract1} 

It  would,  by  reflex  action. 


19°  ANSWERS  TO  PRACTICAL   QUESTIONS 

39.  How  does  one  cough  in  his  sleep  ? 

By  the  reflex  action  of  the  near  nervous  centers.  A 
tickling  in  the  throat,  or  some  other  cause,  acts  as  the 
stimulus  to  excite  their  action. 

40.  Give  illustrations  of  the  unconscious   action   of  the 
brain. 

(See  Physiology,  page  225.) 

194. — i.  Why  does  a  laundress  test  the  temperature  of  her 
flat-iron  by  holding  it  near  her  cheek  ? 

The  sense  of  warmth  is  very  keen  in  the  palms  of  the 
hand,  the  cheek,  etc.  This  sensation  is  much  less  deli- 
cate in  the  lips  and  the  back  of  the  hand. 

2.  When  we  are  cold,  why  do  we  spread  the  palms  of  our 
hands  before  the  fire  ? 

(See  Question  i.) 

3.  What  is  meant  by  a  ''''furred  tongue  ?  " 

In  health,  the  tongue  has  hardly  a  discernible  lining, 
but  in  disease,  the  epithelium,  or  scarf  skin,  accumulates, 
and  gives  a  white,  coated  appearance.  This  covering  is 
likely  to  be  of  a  yellowish  shade  when  the  liver  is  dis- 
turbed, and  brown  or  dark  in  blood  diseases.  One's  oc- 
cupation often  colors  it  Thus  it  is  said  the  tongue  of  a 
tea-taster  has  a  curious  orange-tint. 

4.  Why  has  sand  or  sulphur  no  taste  ? 
They  are  insoluble  in  the  saliva. 

5.  What  was  the  origin  of  the  word  palatable  I 

The  mistaken  notion  that  the  palate,  or  roof  of  the 
mouth,  is  the  seat  of  the  taste. 


IN  HUMAN  PHYSIOLOGY.  IQI 

6.  Why  does  a  cold  in  the  head  injure  the  flavor  of  our 
coffee? 

Because  the  sense  of  taste  is  so  dependent  on  that  of 
smell. 

7.  Name  some  so-called  flavors  which  are  really  sensations 
of  touch. 

Taste  is  not  a  simple  sense.  Certain  other  sensations, 
as  those  of  touch,  temperature,  smell,  and  pain,  are 
blended  and  confused  with  it ;  and  certain  so-called  tastes 
are  really  sensations  of  another  kind.  Thus  an  astrin- 
gent taste,  like  that  of  alum,  is  more  properly  an  astrin- 
gent feeling,  and  results  from  an  impression  made  upon 
the  nerves  of  touch,  that  ramify  in  the  tongue.  In  like 
manner,  the  qualities  known  as  smooth,  oily,  watery,  and 
mealy  tastes,  are  dependent  upon  these  same  nerves  of 
touch.  A  burning  or  pungent  taste  is  a  sensation  of  pain, 
having  its  seat  in  the  tongue  and  throat.  A  cooling  taste, 
like  that  of  mint,  pertains  to  that  modification  of  touch 
called  the  sense  of  temperature.  —  HUTCHISON'S  Phy- 
siology, p.  190-1. 

8.  What  is  the  object  of  the  hairs  in  the  nostrils  ? 

They  prevent  the  entrance  of  dust  and  other  impurities. 
They  are  also  exceedingly  delicate  in  all  sensations  of 
touch. 

9.  What  use  does  the  nose  subserve  in  the  process  of  respi- 
ration ? 

It  warns  us  of  noxious  gases,  sifts  out  impurities,  and 
tempers  the  air  before  it  enters  the  delicate  respiratory 
organs. 


I92  ANSWEHS  TO  PRACTICAL   QUESTIONS 

10.  Why  do  we  sometimes  hold  the  nose  when  we  take 
unpleasant  medicine  ? 

(See  Question  6.) 

11.  Why  is  the  nose  placed  over  the  mouth  ? 

As  a  sentinel  at  the  gateway  to  the  stomach  and  the 
lungs. 

12.  Describe  how  the  hand  is  adapted  to  be  the  instrument 
of  touch. 

Its  isolation  at  the  extremity  of  the  movable  arm,  the 
mobility  of  its  different  parts,  and  the  delicacy  of  the  sen- 
sation at  the  tips  of  the  fingers,  exquisitely  adapt  the 
hand  to  be  the  instrument  of  touch. 

13.  Besides  being  the  organ  of  taste,  what  use  does  the 
tongue  subserve  ? 

It  aids  in  the  mastication  of  the  food  and  in  speech. 

14.  Why  is   not  the  act  of  tasting  complete  until  we 
swallow  ? 

Because  the  organ  of  taste  is  located  especially  in  the 
back  part  of  the  tongue  and  the  soft  palate. 

15.  Why  do  all  things  have  the  same  flavor  when  one's 
tongue  is  "furred"  by  fever  ? 

They  are  really  tasteless.  The  tongue  is  then  dry,  and 
there  is  no  saliva  to  dissolve  and  carry  particles  of  the 
food  into  the  cells  covering  the  nerves  of  taste. 

1 6.  Which  sense  is  the  more  useful — hearing  or  sight? 

(See  Wonders  of  the  Human  Body,  page  201.) 

"The  sight  speaks  more  directly  to  the  intelligence  ;  it 


IN  HUMAN  PHYSIOLOGY.  193 

enlarges  the  field  of  thought,  it  gives  birth  to  precise  no- 
tions of  light,  of  form,  of  extent ;  and  it  permits  the  com- 
munication of  thought  by  conventional  signs.  Hearing  is 
a  necessary  condition  of  articulate  language  ;  without  it 
man  lives  alone,  affection  and  confidence  lose  their  most 
precious  forms  of  expression,  and  friendship  cannot  exist. 
Auditory  sensations  act  upon  the  nervous  system  with 
more  force  than  visual  sensations.  We  are  carried  away 
by  rhythm,  or  it  adapts  itself  to  our  ideas  and  our  passions ; 
music  plunges  us  into  an  ideal  world,  and  holds  us  by  an 
indefinable  charm ;  in  a  word,  if  sight  speaks  more  es- 
pecially to  the  intellect,  hearing  addresses  itself  to  the 
affections.  Sight  is  certainly  more  necessary  to  man  than 
hearing,  but  still  the  blind  are  generally  gay  and  commu- 
nicative, while  the  deaf  seem  inclined  to  melancholy.  As 
to  the  relative  influence  of  these  two  senses  on  the  devel- 
opment of  the  intellect,  we  know  that  the  education  of  the 
deaf  is  slow,  but  may  be  complete,  while  that  of  the  blind 
is,  on  the  contrary,  rather  rapid,  but  is  almost  always  very 
limited ;  many  ideas  cannot  be  acquired  by  them,  and,  as 
has  been  remarked  by  M.  Longet,  their  minds  rarely 
attain  maturity." 

17.  Which  coat  is  the  white  of  the  eye  ? 
The  sclerotic. 

1 8.  What  makes  the  difference  in  the  color  of  eyes  ? 

The  varying  shade  of  the  pigment  deposited  in  the  iris 
of  the  eye. 

19.  Why  do  we  snuff  the  air  when  we  wish  to  obtain  a 
distinct  smell? 

As  muscular  actions  are  called  into  play  to  aid  the 
sense  of  taste,  as  in  smacking  the  tongue  and  lips,  so  the 


J94  ANSWERS  TO  PRACTICAL   QUESTIONS 

act  of  "  sniffing,"  which  is  a  mixed  respiratory  and  nasal 
muscular  effort,  is  used  to  bring  odorous  substances  more 
surely  and  extensively  into  contact  with  the  upper  and 
proper  olfactory  region  of  the  nose,  besides  causing  a 
larger  amount  of  them  to  pass  over  the  mucous  surface  in 
a  given  time. — -MARSHALL. 

20.  Why  do  red-hot  iron  and  frozen  mercury   (—40°) 
produce  the  same  sensation  ? 

The  sensation  in  both  cases  is  that  of  pain,  not  that  of 
touch. 

21.  Why  can  an  elderly  person  drink  tea  which  to  a  child 
would  be  unbearably  hot  ? 

The  sensation  of  touch  has  become  impaired,  and  is 
much  less  delicate. 

22.  Why  does  an  old  man  hold  his  paper  so  far  from  his 
eyes? 

"  Far  sight "  is  common  among  elderly  people,  and  is 
remedied  by  convex  glasses.  In  old  age  the  power  of 
adjusting  the  crystalline  lens  is  lost. 

23.  Would  you   rather  be  punished  on  the  tips  of  your 
fingers  than  on  the  palm  of  your  hand ? 

The  sense  of  touch  is  much  keener  in  the  tips  of  the 
fingers  than  in  the  palm  of  the  hand. 

24.  What  is  the  object  of  the  eyebrows  ?     Are  the  hairs 
straight  ? 

They  serve  to  prevent  the  perspiration  of  the  forehead 
from  running  down  into  the  eye.  They  act,  in  a  measure, 
with  the  eyelashes,  also  to  screen  the  eye  from  the  dust 


%  IN  HUMAN  PHYSIOLOGY.  195 

and  glaring  light.     The  hairs  of  the  eyebrows  overlap 
each  other  and  are  set  obliquely  outward. 

25.  What  is  the  use  of  winking? 

It  serves  to  wash  the  eyeballs,  and  thus  keep  the  "  win- 
dows of  the  soul "  clean.  The  necessity  for  winking  is 
shown  by  the  great  effort  required  to  restrain  it  even  for 
a  short  time.  First  discomfort,  then  congestion  of  the 
mucous  membrane,  and  then  a  profuse  watering  of  the 
eye  follow  any  attempt  at  stopping  this  necessary  act.  It 
is  an  obscure  sense  of  discomfort,  not  usually  noticed  by 
the  consciousness,  that  excites  this  movement,  the  objects 
of  which  are  periodically  to  cleanse  the  exposed  part  of 
the  eyeball,  to  moisten  and  lubricate  it  with  the  secretions 
from  the  neighboring  glands,  and  probably  in  this  way  to 
aid  in  the  preservation  of  the  polish  and  translucency  of 
the  epithelial  layer  on  the  transparent  portion  of  the 
globe.  At  the  same  time  it  carries  towards  the  inner 
corner  all  foreign  bodies,  and  directs  the  residual  secre- 
tions towards  the  lachrymal  ducts.  Finally  it  allows  a 
brief  but  periodical  rest  to  the  levator  muscle  of  the  upper 
eyelid. — MARSHALL. 

26.  When  you  wink,  do  the  eyelids  touch  at  once  along 
their  whole  length  ?     Why  ? 

In  winking,  both  lids  move,  but  the  upper  one  much 
the  more  extensively.  Moreover,  they  do  not  come  in 
contact  all  along  their  margins  at  the  same  instant  of 
time,  but  meet  first  at  the  outer  corner  and  then  rapidly 
inwards  as  far  as  the  lachrymal  papillae  on  which  the  lach- 
rymal ducts  are  situated.  By  this  sweeping  movement,  all 
foreign  bodies  are  carried  to  the  lachrymal  lake. — MAR- 
SHALL. 


196  ANSWEMS   TO  PRACTICAL   QUESTIONS  * 

27.  How  many  rows  of  hairs  are  there  in  the  eyebrows  ? 

The  eyelashes,  or  cilia,  consist  of  two,  and  opposite  the 
middle  of  the  eyelid,  of  three  rows  of  finely-curved  hairs 
— those  of  the  upper  lid  being  more  numerous,  thicker, 
and  longer  than  those  of  the  lower  lid.  "  Those  of  the 
upper  lid  are  curved  upward,  those  of  the  lower  lid  are 
curved  downward ;  and  when  the  lids  are  brought  near 
together,  these  two  ranges  of  hairs  stand  like  so  many 
crossed  sabres,  or  a  kind  of  chevaux-de-frise,  guarding 
the  entrance  to  the  eye." — DALTON'S  Physiology,  p.  330. 

28.  Do  all  nations  have  eyes  of  the  same  shape  ? 

No.  Witness  the  almond-shaped  eyes  of  the  Chinese. 
"  The  greater  or  less  extent  of  the  opening  of  the  lids 
makes  the  eye  appear  larger  or  smaller  ;  the  conforma- 
tion of  the  palpebral  muscles  and  the  tarsal  cartilages 
gives  to  the  eye  an  elongated  and  languishing  form  as  in 
the  East,  or  round  and  bold  as  among  the  Occidentals ; 
but  the  dimensions  and  form  of  the  globe  are  the  same  in 
all  countries  and  in  all  individuals." —  Wonders  of  the 
Human  Body. 

29.  Why  does  snuff-taking  cause  a  flow  of  tears  ? 
Because  of  the  action  of  the  sympathetic  system. 

30.  Why  does  a  fall  cause  one  to  "  see  stars  ?"* 

Whenever  a  nerve  is  excited  in  any  way,  it  gives  rise 
to  the  sensation  peculiar  to  the  organ  with  which  it  com- 

*  u  On  the  occasion  of  a  remarkable  trial  in  Germany,  it  was  claimed  by  a 
person  who  had  been  severely  assaulted  on  a  very  dark  night,  that  the  flashes 
of  light  caused  by  repeated  blows  upon  the  head  enabled  him  to  see  with 
sufficient  distinctness  to  recognize  his  assailant.  But  the  evidence  of  scien- 
tific men  entirely  refuted  this  claim,  by  pronouncing  that  the  eye,  under  the 
circumstances  named,  was  incapacitated  for  vision."— HUTCHISON. 


IN  HUMAN  PHYSIOLOGY.  1 97 

municates.  Thus,  an  electric  shock  sent  through  the  eye 
gives  rise  to  the  appearance  of  a  flash  of  light ;  and  pres- 
sure on  any  part  of  the  retina  produces  a  luminous  image, 
which  lasts  as  long  as  the  pressure,  and  is  called  -a.phos~ 
phene.  If  the  point  of  the  finger  be  pressed  upon  the 
outer  side  of  the  ball  of  the  eye,  a  luminous  image — 
which,  in  my  own  case,  is  dark  in  the  centre,  with  a  bright 
ring  at  the  circumference  (or,  as  Newton  described  it,  like 
•the  "eye"  in  a  peacock's  tail) — is  seen;  and  this  image 
lasts  as  long  as  the  pressure  is  continued. — HUXLEY. 

31.  Why  can  we  not  see  with  the  nose,  or  smell  with  the 
eyes  ? 

Each  set  of  nerves  is  adapted  to  transmit  to  the  brain  a 
peculiar  class  of  sensations  alone. 

32.  What  causes  the  roughness  of  a  cat's  tongue  ? 

The  sharpness  and  strength  of  the  papillae  upon  its 
tongue.  This  is  a  peculiarity  of  the  lion  tribe. 

33.  Is  the  cuticle  essential  to  touch  ? 

Yes.  If  the  cuticle  be  removed,  as  in  case  of  a  blister, 
contact  with  the  exposed  surface  produces  pain  rather 
than  a  sense  of  touch. 

34.  Can  one  tickle  himself  1 

It  is  said  not ;  but  the  author  has  found  persons  who 
averred  that  they  could  produce  this  sensation  upon  them- 
selves. The  sense,  it  is  noticeable,  is  present  only  in  those 
parts  where  that  of  touch  is  feeble. 

35.  Why  does  a  bitter  taste  of  ten  produce  vomiting? 
The  5th  pair  of  nerves,  which  supplies  the  lip  and  sides 


19**  ANSWERS  TO  PRACTICAL   QUESTIONS 

of  the  tongue,  and  perceives  especially  sweet  and  sour 
substances,  ramifies  over  the  face,  and  hence  an  acid  will 
"pucker"  the  features ;  while  the  gth  pair,  at  the  base  of 
the  tongue,  which  is  sensitive  to  salt  and  bitter  tastes,  is 
distributed  also  to  the  throat,  and  is  in  sympathy  with  the 
internal  organs,  since  it  seems  to  be  "  a  common  nerve  of 
feeling  for  the  mucous  membrane  generally." 

36.  Is   there  any   danger  of  looking  "cross-eyed"  for 
fun? 

The  muscles  used  thus  in  sport  may  become  perma- 
nently distorted. 

37.  Should  school-room  desks  face  a  window  ? 

No.  The  light  should  be  admitted  so  as  to  fall  over 
the  shoulder  upon  the  book.  Many  school-rooms  are 
arranged  to  accommodate  the  teacher  only,  while  a  blind- 
ing flood  of  light  pours  directly  into  the  faces  of  the 
pupils. 

38.  Why  do  we  look  at  a  person  to  whom  we  are  listening 
attentively  ? 

One  sense  instinctively  aids  another. 

39.  Do  we  really  feel  with  our  fingers  ? 
No.     All  sensation  is  in  the  mind. 

40.  Is  the  eye  a  perfect  sphere  ? 

No.  The  front  projects  somewhat,  while,  at  the  back, 
ihe  optic  nerve  is  attached  like  the  stem  to  a  fruit. 


IN  HUMAN  PHYSIOLOGY.  199 

41.  How  often  do  we  wink  ? 
Five  or  six  times  a  minute. 

42.  Why  is  the  interior  of  a  telescope  or  microscope  often 
painted  black  1 

To  absorb  the  scattered  rays  of  light  which  would 
confuse  the  vision.  For  the  same  reason,  the  posterior 
'surface  of  the  iris,  the  ciliary  processes  and  the  choroid 
are  covered  with  a  layer  of  dark  pigment. 

43 .  What  is  "  the  apple  of  the  eye  ?" 
The  pupil. 

44.  What  form  of  glasses  do  old  people  require  ? 

(See  Question  22.) 

45.  Should  we  ever  wash  our  ears  with  cold  water? 
Rarely,  if  ever,  lest  we  chill  this  sensitive  organ. 

46.  What  is  the  object  of  the  winding  passages  in  the 
nose? 

To  furnish  additional  surface  on  which  to  expand  the 
olfactory  nerve. 

47.  Can  a  smoker  tell  in  the  dark,  whether  or  not  his 
cigar  is  lighted? 

Sight  often  seems  to  be  essential  to  perfect  what  we 
call  a  sensation  of  taste. 

48.  Will  a  nerve  re-unite  after  it  has  been  cut  ? 
Nerve-fibre  seems  to  re-unite  as  readily  as  muscle-fibre. 


200  ANSWERS  TO  PRACTICAL   QUESTIONS. 

49.  Will  the  sight  give  us  an  idea  of  solidity  ? 

(See  Physiology,  page  196,  note.) 

50.  Why  can  a  skillful  surgeon  determine  the  condition  of 
the  brain   and  other  internal  organs  by  examining  the  in- 
terior of  the  eye  ? 

(See  Physiology,  page  196,  note.) 

51.  Is  there  any  truth  in  the  idea  that  the  image  of  the 
murderer  can  be  seen  in  the  eye  of  the  dead  victim  ? 

When  the  flame  of  a  taper  is  held  near,  and  a  little  on 
one  side  of,  a  person's  eye,  any  one  looking  into  the  eye 
from  a  proper  point  of  view  will  see  three  images  of  the 
flame,  two  upright  and  one  inverted.  One  upright  figure 
is  reflected  from  the  front  of  the  cornea,  which  acts  as  a 
convex  mirror.  The  second  proceeds  from  the  front  of 
the  crystalline  lens,  which  has  the  same  effect ;  while  the 
inverted  image  proceeds  from  the  posterior  face  of  the 
lens,  which,  being  convex  backwards,  is,  of  course,  con- 
cave forwards,  and  acts  as  a  concave  mirror. — HUXLEY. 
The  images  formed  upon  the  retina  are  as  fleeting  as  light 
itself,  from  the  nature  of  the  case,  and  disappear  as  soon 
as  the  object  is  removed. 


ANSWERS 

TO  THE 

PEACTICAL  QUESTIONS  AND   PEOBLEMS 

IN  THE 

FOURTEEN  WEEKS  COURSE  IN  PHYSICS, 


MOTION   AND   FORCE.  * 

37. — 1-37.  (See  pp.  15-19  of  this  Key  for  Answers  to 
these  Questions.) 

38.  If  a  100  horse-power  engine  can  propel  a  steamer  5 
miles  per  hour,  will  one  0/200  horse-power  double  its  speed? 

By  no  means.  Resistance  is  proportional  to  zf*.  (See 
Physics,  p.  26.)  To  double  the  velocity  would  require 
over  400  horse-power.  (See  note,  p.  27.) 

39.  Why  is  a  bullet  flattened  if  fired  obliquely  against 
the  surface  of  water  ? 

"  Because  the  particles  of  the  ball  which  strike  the 
water  are  impeded  in  their  course  by  the  particles  of 
water  with  which  they  come  in  contact,  and  are  driven 
back  upon  those  lying  next  to  them,  before  the  motion  of 
the  ball  can  be  imparted  to  the  water  " — A.  B.  Watkins. 


202  ANSWERS  TO  PRACTICAL   QUESTIONS 

40.  Why  are  ships  becalmed  at  sea  of  ten  floated  by  strong 
currents  into  dangerous  localities  without  the  knowkdge  of 
the  crew  ? 

As  there  are  no  fixed  objects  with  which  to  compare 
their  motion,  the  officers  are  not  sensible  of  any  move- 
ment, and  so  are  often  drifted  far  out  of  their  course. 

41.  A  man  in  a  wagon  holds  a  $o-lb.  weight  in  his  hand. 
Suddenly  the  wagon  falls  over  a  precipice.      Will  he,  while 
dropping,  bear  the  strain  of  the  weight  ? 

No.  While  on  solid  ground,  his  hand  resisted  the 
tendency  of  the  weight  to  fall  toward  the  earth's  centre 
of  gravity ;  but  all  are  now  descending  freely  under  the 
influence  of  gravity,  and  he  no  longer  feels  the  pressure. 

42.  Why  are  we  not  sensible  of  the  rapid  motion  of  the 
earth  ? 

Because  all  the  objects  around  us  are  moving  in  the 
same  direction  with  the  earth,  and  there  is  nothing  at 
hand  with  which  to  compare. 

43.  A  feather  is  dropped  from  a  balloon  which  is  im- 
mersed in  and  swept  along  by  a  swift  current  of  air.      Will 
the  feather  be  blown  away,  or  will  it  appear  to  a  person  in 
the  balloon  to  drop  directly  down  ? 

It  will  seem  to  drop  directly  downward,  as  if  in  a  dead 
calm.  Its  fall  is  vertical,  however,  only  as  regards  the 
balloon,  and  not  as  regards  the  earth. 

(See  Stewart's  Physics,  p.  18.) 

44.  Suppose  a  bomb-shell,  flying  through  the  air  at  the 
rate  of  500  feet  per  second,  explodes  into  two  parts  of  equal 
weight,  driving  one-half  forward  in  the  same  direction  as 


IN  PHYSICS.  203 

before,  but  with  double  its  former  velocity.      What  would 
become  of  the  other  half? 

One  half  will  go  forward  with  a  double  velocity 
(=1000  feet  per  sec.),  and  the  other  half  will  be  checked 
and  will  fall  directly  to  the  ground. 

(See  Stewart's  Physics,  p.  37.) 

45 .  Which  would  have  the  greater  penetrating  power,  a 
small  cannon-ball  with  a  high  velocity,  or  a  large  one  with 
a  low  velocity  ? 

The  former  would  penetrate,  while  the  latter  would 
crush  an  obstacle. 

46.  There  is  a  story  told  of  a  man  who  erected  a  huge 
pair  of  bellows  in  the  stern  of  his  pleasure-boat,  that  he 
might  always  have  a  fair  wind.     On  trial,  the  plan  failed. 
In  which  direction  should  he  have  turned  the  bellows  ? 

(See  Key,  p.  20.) 

47.  If  a  man  and  a  boy  were  riding  in  a  wagon,  and, 
on  coming  to  the  foot  of  a  hill,  the  man  should  take  up  the 
boy  in  his  arms,  would  that  help  the  horse  ? 

No  change  would  be  produced  in  the  weight  of  the 
entire  establishment  drawn  by  the  horse,  as  no  readjust- 
ment of  the  load  would  modify  the  attraction  of  gravity 
which  produces  the  weight.  Also,  action  =:  reaction ;  so 
the  man  would  press  down  on  the  wagon  an  amount 
equal  to  the  weight  of  the  boy. 

48.  Why  does  a  bird,  as  it  begins  to  fly,  always,  if  pos- 
sible, turn  toward  the  wind  ? 

For  the  same  reason  that  a  boy,  wishing  to  raise  a  kite, 
runs  against  the  wind.  The  greater  the  velocity  of  the 
wind,  within  certain  limits,  the  greater  the  lifting  force. 

(See  note,  p.  32.) 


204  ANSWERS  TO  PRACTICAL   QUESTIONS 

49.  If  we  whirl  a  pail  of  water  swiftly  around  with 
our  hands,  why  will  the  water  tend  to  leave  the  centre  of  the 
pain 

This  is  generally  attributed  to  the  action  of  the  cen- 
trifugal force.  More  correctly,  the  inertia  of  the  water, 
i.e.,  its  tendency  to  continue  to  move  in  the  straight 
line  in  which  it  is  at  each  moment  passing,  overcomes 
the  weak  force  of  cohesion,  and  the  molecules  fly  off 
from  the  centre  of  motion  and  collect  against  the  outside 
of  the  pail. 

50.  Why  will  the  foam   collect  at  the  hollow  in  the 
centre  ? 

The  foam,  being  lighter  than  the  water,  has  less  mo- 
mentum, and  is  forced  back  by  the  heavier  particles. 

51.  If.  two  cannon-balls,  one  weighing  8  Ibs.  and  the 
other  2  Ibs.,  be  fired  with  the  same  velocity,  which  will  go 
the  further1} 

The  former  has  much  less  surface  in  proportion  to  its 
weight  and  consequent  momentum.  It  will  therefore  go 
much  further  against  the  resistance  of  the  air. 

52.  Resolve  the  force  of  the  wind  which  turns  a  common 
wind-mill,  and  show  how  one  part  acts  to  push  the  wheel 
against  its  support,  and  one  to  turn  it  around. 

(See  Arnott's  Physics,  p.  226.) 

The  toy-mill  shown  in  Fig.  14,  p.  32,  illustrates  the 
principle  perfectly.  The  vanes  turn  in  a  direction  con- 
trary to  that  in  which  they  are  inclined.  Let  GH,  in  Fig. 
10,  p.  31,  represent  the  face  of  the  vane,  and  the  descrip- 
tion in  the  text  will  then  apply. 


IN  PHYSICS.  205 

53.  Why  is  a  gun  firing  blank  cartridges  more  quickly 
heated  than  one  firing  balls  ? 

In  the  one  case,  the  energy  of  the  burning  powder  is 
changed  to  heat ;  in  the  other,  largely  to  the  motion  of 
the  ball. 

54.  When  an  animal  is  jumping  or  falling,  can  any 
exertion  made  in  mid-air  change  the  motion  of  its  centre  of 
gravity  ? 

The  centre  of  gravity  falls  steadily  16.08  feet  (see 
P-  54)>  whatever  other  force  may  act  on  the  body. 

(See  Second  Law  of  Motion.) 

55-60.  (See  Answers  under  Questions  i  to  7,  on  pages 
5  and  6  of  this  Key.) 

61.  Why  is  a  "  running  jump  "  longer  than  a  "  standing 
jump  "? 

This  is  generally  spoken  of  as  an  illustration  of  inertia. 
It  is  really  an  example  under  the  first  law  of  motion. 
The  momentum  of  the  person  when  running  (m  x  v)  is 
added  to  the  force  with  which  he  finally  springs  from  the 
ground  for  the  jump. 

62.  Why,  after  the  sails  of  a  vessel  are  furled,  does  it 
still  continue  to  move  ?   and  why,  after  the  sails  are  spread, 
does  it  require  some  time  to  get  it  under  full  headway  ? 

This  illustrates  the  tendency  of  matter  to  continue  in 
its  present  state,  whether  of  rest  or  of  motion,  i.  e.,  its 
inertia.  For  the  former  part  of  the  question,  apply  the 
first  law  of  motion,  and  for  the  latter,  the  first  paragraph 
on  p.  28  of  the  Physics.  If,  on  starting  with  a  heavy 
load,  the  horses  leap  suddenly  forward,  they  will  break 


206  ANSWERS  TO  PRACTICAL   QUESTIONS 

the    harness;    but,   by    a    steady,    constantly-increased 
draught,  they  will  overcome  the  inertia  of  the  mass. 

63.    Why  can  a  tallow  candle  be  fired  through  a  board? 

Because  it  pierces  the  board  so  quickly  that  the  par- 
ticles have  no  time  to  yield.  Its  slight  cohesion,  multi- 
plied by  its  velocity,  is  greater  than  the  cohesion  of  the 
board. 

COHESION. 

46. — i-io.  (See  Answers  to  these  Questions  under 
Cohesion,  pp.  6  and  7  of  this  Key.) 

1 1 .    Why  can  glass  be  welded  ? 

Because,  like  iron,  it  becomes  viscous  before  melting. 


ADHESION. 

51. — 1-17.  (See  Answers  to  these  Questions  under 
Adhesion,  pp.  7  to  9  of  this  Key.) 

1 8.  Why  does  the  water  in  Fig.  22  stand  higher  inside 
of  the  tube  than  next  the  glass  on  the  outside  ? 

There  is  the  influence  of  a  larger  surface  of  glass  in 
proportion  to  the  quantity  of  water  to  be  lifted. 

19.  Why  will  clothes-lines  tighten  and  sometimes  break 
during  a  shower  ? 

The  rope  absorbs  water  and  expands  transversely. 
This  shortens  it  with  so  much  force  as  often  to  break  it. 
The  shrinking  of  new  cloth  when  wet  illustrates  the  same 
principle. 


IN  PHYSICS.  207 

20.  Show  that  the  law  of  the  diffusion  of  gases  aids  in 
preserving  the  purity  of  the  atmosphere. 

(See  New  Chemistry,  p.  96.) 

Foul  gases  do  not  remain  for  any  length  of  time  in  one 
place,  but  tend  to  spread  through  the  adjacent  atmos- 
phere. Fresh  air  also  seeks  to  creep  into  noisome 
localities. 

21.  In  casting  large  cannon,  the  gun  is  cooled  by  a  stream 
of  cold  water.     Why  ? 

The  object  of  this  is  to  cause  the  iron  to  cool  more 
quickly  and  so  not  give  the  molecules  time  to  arrange 
themselves  in  crystals. 

(See  p.  45.) 

22.  Why  does  paint  adhere  to  wood?     Chalk  to  the 
blackboard  ? 

These  are  illustrations  of  the  force  of  adhesion. 

23.  Why  does  a  towel  dry  one's  face  after  washing1} 

The  capillary  pores  of  the  cloth  absorb  the  water  on 
the  face. 

24.  Why  will  a  greased  needle  float  on  water  ? 

The  repulsion  between  the  grease  and  the  water  is 
sufficient  to  support  the  slight  weight  of  the  needle. 

2  5 .    Why  is  the  point  of  a  pen  slit  ? 

The  ink  rises  in  the  capillary  space  of  the  slit,  and  is 
there  held  for  use.  When  the  pen  is  pressed  on  the 
paper,  the  space  is  widened  and  the  ink  descends. 

26.  Why  is  a  thin  layer  of  glue  stronger  than  a  thick 
one? 


208  ANSWERS  TO  PRACTICAL  QUESTIONS 

The  adhesion  between  the  glue  and  the  wood  is 
stronger  than  the  cohesion  between  the  particles  of 
glue ;  hence  the  thinner  the  layer  of  glue  the  fewer  the 
particles  acted  upon  only  by  the  latter  or  weaker  force. 


GRAVITATION. 

62. — 1-41.  (See  the  Answers  to  these  Queries  on  pp. 
9  to  14  of  this  Key.) 

42.  How  long  would  it  take  for  a  pendulum  one  mile  in 
length  to  make  a  vibration  ? 

(See  Key,  p.  13,  Problem  37.) 

According  to  the  second  law  of  pendulums  (Physics, 
P-  59), 

i  sec.  :  x  : :  A/39  :  ^5280  x  12  in. 
x  —  40  -f  sec. 

43.  How  long  would  it  take  for  a  pendulum  reaching 
from  the  earth  to  the  moon  to  make  a  vibration  ? 


i  sec.  :  x  : :  A/39-i  in.  :  \/24o,ooo  x  5280  x  12  in. 
x  =  5  hrs.  28  -+-  minutes. 

44.  Required  the  length   of   a  pendulum   that  would 
vibrate  centuries. 

(i  sec.)2  :  (100  x  365.25  x  24  x  60  x  60)^  : :  39.1  in.  :  x. 
x  =  6,145,674,053,727,272  +  miles. 

— SOLOMON   SIAS. 

45.  What  would  be  the  time  of  vibration  of  a  pendulum 
64  metres  long  ? 

(i  sec.)2  :  x*  : :  i  metre  (nearly)  :  64  metres. 
x  =  8  seconds  (nearly). 


PHYSICS. 


209 


46.  A  ball  is  dropped  from  a  height  of  64  feet.     At  the 
same  moment  a  second  ball  is  thrown  upward  with  sufficient 
velocity  to  reach  the  same  point.      Where  will  the  two  balls 
pass  each  other  ? 

At  the  end  of  one  second.  The  first  ball  would  fall 
64  feet  in  2  seconds ;  the  second  would  rise  for  2  sec- 
onds, and  they  would  pass  in  i  sec. 

47.  Two  bodies  are  successively  dropped  from  the  same 
point  with  an  interval  of  \  of  a  second.      When  will  the 
distance  between  them  be  one  metre  ? 

Let  /  =  time  of  descent  of  2d  body. 
Then  /-f  .2  =  time  of  descent  of  ist  body. 

Since  the  space  passed  over  equals  4.9  m.  (16  ft.)  mul- 
tiplied by  the  square  of  the  time,  we  have 

4.9  /2  =  space  passed  over  by  2d  body. 
4.9(/  +  -2)2  =  4-9'2  +  1-96'  +  .196 

=  space  passed  over  by  ist  body. 

The  difference  between  the  2   spaces  being  i   m.,  we 

have 

4.9/2  +  i.96/  +  .196  —  4.9/2  =  i  m. 

i.96/  =  .804. 

/  =  .4102  sec.  =  time  of  descent  of  2d  body. 
.6102  sec.  =  time  of  descent  of  ist  body. 

Therefore  they  will  be  i  m.  apart  when  the  ist  body  has 
fallen  for  .6102  sec.,  or  the  2d  body  for  .4102  sec. 

PROOF. — 4.9  x  .6io22  —  4.9  x  .4io22  —  i  (nearly). 

— WM.  H.  TAYLOR. 

48.  Explain  the  following  fact :    A  straight  stick  loaded 
with  lead  at  one  end,  can  be  more  easily  balanced  vertically 


210  ANSWERS  TO  PRACTICAL   QUESTIONS 

on  the  finger  when  the  loaded  end  is  upward  than  when  it 
is  downward. 

When  the  loaded  end  is  upward  a  slighter  motion  is 
needed  to  bring  the  line  of  direction  within  the  base. 
The  principle  is  similar  to  that  of  the  balancing  pole  of 
the  gymnast. 

49.  What  effect  would  the  fall  of  a  heavy  body  to  the 
earth  have  upon  the  motion  of  the  earth  in  its  orbit? 

If  its  line  of  fall  was  exactly  opposed  to  the  direction 
of  the  earth's  motion,  it  would,  by  its  momentum,  tend 
to  retard  the  earth.  If  its  line  of  fall  was  exactly  in  the 
direction  of  the  earth's  motion,  it  would  increase  the 
earth's  velocity.  If  its  line  of  fall  was  transverse  to 
the  direction  of  the  earth's  motion,  it  would  deflect  the 
earth  from  its  orbit.  All  of  these  changes  would,  of 
course,  be  infinitesimal  in  amount. 

50.  If  a  body  weighing  i  Ib.  on  the  earth  were  carried 
to  the  sun,  it  would  weigh  27  Ibs.     How  much  would  it 
attract  the  sun  ? 

Ans.  27  Ibs. 

5 1.  Why  does  watery  vapor  float  and  rainfall? 

(See  Physics,  p.  116,  Question  13.) 

The  vapor  of  water  is  lighter  than  water  itself,  as  the 
particles  are  pushed  so  far  apart  by  the  repellent  force — 
heat. 

52.  If  a  body  weighs  10  kilos,  on  the  surface  of  the  earth, 
what  will  it  weigh  1,000  km.  above? 

x:  10  kilos.  ::  (6,366  *)2:  (7.366)2 
x  —  7.5  kilograms. 

*  The  radius,  or  semi-diameter  of  the  earth,  is  given  by  French  astronomers 
at  6,366  km. 


IN  PHYSICS.  211 

53.  A  body  is  thrown  vertically  upward  with  a  velocity 
of  100   metres.      How  long  before  it  will  return   to  its 

original  position  ? 

Ans.  20.4  seconds. 

54.  How   long  will  be  required  for  a  body  to  fall  a 
distance  of  2,000  metres  ? 

Equation  (6)         d  =  \gt 2.         2,000  =  -— 1\ 
.*.  /  =  20.2  seconds. 

55.  If  two  bodies   weighing  respectively    i    kilo,  and  i 
demi-kilo.  are  connected  by  a  rod  9  decimetres  long,  where  is 
the  centre  of  gravity  ? 

Ans.  6  dm.  from  one  body  and  3  dm.  from  the  other. 

(See  Key,  p.  10,  Question  7.) 

ELEMENTS   OF   MACHINES. 

79. — 1-26.  (See  Answers  on  pp.  20  to  24  of  this 
Key.) 

27.  Why  is  the  rim  of  a  fly-wheel  made  so  heavy  ? 

The  heavier  the  wheel,  the  greater  its  inertia ;  and  the 
further  the  weight  is  from  the  centre  of  motion  (or  axle), 
the  greater  its  inertia  or  centrifugal  force. 

(See  Physics,  p.  78.) 

28.  Describe  the  hammer,  when  used  in  drawing  a  nail, 
as  a  bent  lever,  i.  e.,  one  in  which  the  bar  is  not  straight. 

If  a  lever  is  bent,  or  if,  when  it  is  straight,  the  bar  is 
not  at  right  angles  to  the  lines  of  action  of  the  P  and 
the  W,  it  is  necessary  to  distinguish  between  the  arms  of 


212  ANSWERS  TO  PRACTICAL  QUESTIONS 

a  lever'  and  the  arms  of  the  P  and  the  W,  regarded  as 
forces  which  have  moments  around  the  F.  In  the  latter 
sense,  the  arms  are  the  perpendiculars,  dropped  from  the 
F  to  the  lines  of  action  of  the  P  and  the  W. 

(See  Everett's    Text-book  of  Physics,  p.  23  ;    and  Todhunter's  Natural 
Philosophy  for  Beginners,  Vol.  I,  p.  78,  where  there  is  an  excellent  diagram.) 


HYDROSTATICS. 

96. — 1-38.  (See  pp.  24-29  of  this  Key.) 

39.  Suppose  that  Hiertfs  crown  was  an  alloy  of  silver 
and  gold,  and  weighed  22  ozs.  in  air  and  20 \  ozs.  in  water. 
What  was  the  proportion  of  each  metal? 

"  Multiply  the  specific  gravity  of  each  ingredient  by 
the  difference  between  it  and  the  specific  gravity  of  the 
compound.  As  the  sum  of  the  products  is  to  the  respec- 
tive products,  so  is  the  specific  gravity  of  the  body  to  the 
proportions  of  the  ingredients.  Then,  as  the  specific 
gravity  of  the  compound  is  to  the  weight  of  the  com- 
pound, so  is  each  of  the  proportions  to  the  weight  of  its 
material. ' ' — American  Cyclopcedia. 

Second  method : 

Let  A  —  mass  of  crown  =  22 
"     B  =  sp.  gr.         "      =  14.66 
"    *  =  mass  of  gold 
"    #'  =  sp.  gr.       "        =  19.26 
"    y   =  mass  of  silver 

"    /  =  sp.  gr.        "        =  10.5 
then 

A  =  #  + 


IN  PHYSICS,  213 

and  since 

mass 
volume  — 


specific  gravity ' 
we  have 

A  _  *  ,  y_. 

B  ~  x  +  / ' 
whence  we  find  (approximately), 

Gold    =  13.95 
Silver  =    8.05 

40.  Why  will  oily  which  floats  on  water,  sink  in  alco- 
hol ? 

The  specific  gravity  of  absolute  alcohol  is  only  .79 ; 
hence  even  the  dilute  alcohol  of  commerce  is  lighter 
than  water. 

41.  A  specific-gravity  bottle  holds  100  gms.  of  water  and 
1 80  gms.  of  sulphuric  acid.     Required  the  density  of  the 
acid. 

Ans.   1.8. 

42.  What  is  the  density  of  a  body  which  weighs  58  gms. 
in  air  and  46  gms.  in  water  ? 

Ans.  4f. 

43.  What  is  the  density  of  a  body  which  weighs  63  gms. 
in  air  and  35  gms.  in  a  liquid  of  a  density  of  3>$  ? 

Ans.  1.9125. 

HYDRAULICS  OR  HYDRODYNAMICS. 
103.— 1-5.  (See  Key,  pp.  29,  30.) 


214  ANSWERS  TO  PRACTICAL  QUESTIONS 

PNEUMATICS. 
116. — 1-18.  (See  Key,  pp.  30-32.) 

19.  Explain  the  theory  of  " sucking  cider"   through  a 
straw. 

The  air  in  the  straw  being  exhausted,  the  pressure  of 
the  air  on  the  cider  in  the  vessel  forces  the  liquid  through 
the  straw. 

20.  Would  it  make  any  difference  in  the  action  of  the 
siphon  if  the  arms  were  of  unequal  diameter  ? 

It  would  change  the  relative  weight  of  the  columns  of 
liquid  in  the  two  arms,  and  so  increase  or  diminish  the 
difference  of  pressure  which  forces  the  liquid  through 
the  long  arm.  Now,  the  heavier  cd  and  the  lighter  ab^  in 
Fig.  105,  the  faster  the  flow. 

21.  If  the  receiver  of  an  air-pump  is  5  times  as  large  as 
the  barrel,  how  many  strokes  of  the  piston  will  be  needed  to 
diminish  the  air  nearly  one-half! 

One-fifth  of  the  air  in  the  receiver  is  removed  at  each 
stroke.  After  the  third  stroke  there  would  remain  in  the 
receiver  -ff^  of  the  original  atmosphere. 

22.  What  would  be  the  effect  of  making  a  small  hole  in 
the  top  of  a  diving-bell  while  in  use  ? 

The  air  would  escape  at  the  top,  and  the  water  would 
ascend  and  fill  the  bell. 

ACOUSTICS. 
144.— 1-16.  (See  Key,  pp.  32-34.) 


IN  PHYSICS  215 

17.  Why  will  the  report  of  a  cannon  fired  in  a  valley  be 
heard  on  the  top  of  a  neighboring  mountain,  better  than  one 
fired  on  the  top  of  a  mountain  will  be  heard  in  the  valley  ? 

A  sound  always  has  the  intensity  given  it  by  the 
density  of  the  atmosphere  where  it  originated,  and  not  of 
that  where  it  is  heard. 

(See  Tyndall's  Lectures  on  Sound,  p.  40.) 

1 8.  Why  do  our  footsteps  in  unfurnished  dwellings  sound 
so  startlingly  distinct  t 

In  furnished  rooms,  the  chairs,  carpets,  pictures,  etc. 
break  up  the  echoes.  Then,  also,  our  footsteps  are 
louder  on  an  uncarpeted  floor. 

19.  Why  do  the  echoes  of  an  empty  church  disappear 
when  the  audience  assemble  ? 

The  audience  break  up  the  echoes  which  interfere  with 
the  original  sound.  Wires  strung  across  a  lofty  room 
often  serve  the  same  purpose. 

20.  What  is  the  object  of  the  sounding-board  of  a  piano  ? 

By  its  vibrations  and  those  of  the  body  of  air  which 
it  encloses,  it  reinforces  the  sound  of  the  wires. 

21.  During  some  experiments,    Tyndall  found  that  a 
certain  sound  would  pass  through  twelve  folds  of  a  dry  silk 
handkerchief,  but  would  be  stopped  by  a  single  fold  of  a  wet 
one.     Explain. 

(See  Tyndall's  Lectures  on  Light,  p.  325,  for  a  series  of  experiments 
showing  the  action  of  moisture  in  propagating  the  sound-waves.) 

22.  What  is  the  cause  of  the  musical  murmur  often 
heard  near  telegraph  lines  ? 


2l6  ANSWERS  TO  PRACTICAL   QUESTIONS 

It  is  produced  by  the  vibration  of  the  wires.     These 
are  thrown  into  motion  by  the  wind  and  other  causes. 

23.  Why  will  a  variation  in  the  quantity  of  water  in  the 
goblet,  when  caused  to  sound  as  in  the  experiment  described 
on  page  123,  make  a  difference  in  the  tone  / 

It  changes  the  length  of  the  vibrating  portion  of  the 
glass. 

24.  At  what  rate  (in  metres)  will  sound  move  through 
air  at  20° CJ 

Sound  moves  at  the  rate  of  1,090  feet  at  o°  C.    The 
difference  is  nearly  2  feet  for  each  degree  C. 

1090  feet  +  40  feet  =1130  feet. 


OPTICS. 

177.— 1-25.  (See  Key,  pp.  35-39.) 

26.  What  is  the  principle  of  the  kaleidoscope? 

27.  Which  will  be  seen  at  the  greater  distance,  a  yellow 
or  a  gray  body  ? 

The  yellow,  since  it  is  brighter. 

28.  Look  down  into  the  glass  of  water  shown  in  fig.  145, 
and  at  a  certain  angle  you  will  see  two  spoons,  one  small 
and  having  the  real  handle  of  the  spoon,  though  apparently 
bent,  and  the  real  spoon  with  no  handle.     Explain. 

In  trying  the  experiments  here  alluded  to,  the  glass 
should  be  looked  into  at  all  possible  angles,  and  the 
spoon  be  turned  about  in  the  goblet.  The  glass  of  water 
acts  as  a  convex  lens  to  magnify  objects ;  the  concave 


IN  PHYSICS.  217 

upper  surface  of  the  water,  when  one  looks  down  into  it, 
as  a  concave  lens  to  minify  objects ;  and  the  upper  sur- 
face of  the  water,  when  one  looks  up  at  it,  as  a  total 
reflector  of  the  light.  These  facts,  together  with  the 
phenomenon  of  refraction,  as  shown  in  the  apparent 
breaking  of  the  handle  where  it  enters  the  water,  will 
account  for  all  the  curious  modifications  which  may  be 
noticed.  The  experiment  is  worth  hours  of  examina- 
tion. 

29.  When  a  star  is  near  the  horizon,  does  it  seem  higher 
or  lower  than  its  true  place? 

It  seems  higher,  since  the  rays  of  light  are  bent 
downward  to  the  eye,  and  the  object  is  seen  in  the  line 
of  the  ray  as  it  enters  that  organ. 

30.  Why  can  we  not  see  a  rainbow  at  midday  ? 

Because  the  sun  is  not  in  the  right  position.  To  pro- 
duce the  ordinary  rainbow  it  must  be  toward  the  eastern 
or  western  horizon. 

31.  What  conclusion  do  we  draw  from   the  fact  that 
moonlight  shows  the  same  dark  lines  as  sunlight  / 

That  its  light  has  the  same  source  as  that  of  the  sun, 
and  is,  indeed,  sunlight. 

32.  Why  does  the  bottom  of  a  ship  seen   tinder  water 
appear  flatter  than  it  really  is  ? 

Because,  by  refraction,  the  bottom  of  the  ship  is 
apparently  elevated  above  its  true  place. 

33.  Of  what  shape  does  a  round  body  appear  in  water? 

It  appears  to  be  flattened ;  and  hence  a  round  body 
looks  like  an  oval  one. 


2l8  ANSWERS  TO  PRACTICAL   QUESTIONS 

34.  Why  is  rough  glass  translucent  while  smooth  glass  is 
transparent  ? 

.  The  minute  protuberances  scatter  the  rays  of  light 
and  do  not  allow  them  to  pass  freely  to  the  eye  of  the 
observer. 

35-42.  (See  Key,  pp.  38,  39  ;  Questions  28-35.) 

43.  Are  there  rays   in   the  sunbeam  which  we  cannot 
perceive  with  the  eye  ? 

(See  Physics,  pp.  163,  164.) 

The  calorific  and  actinic  rays  are  invisible. 

44.  Why,  when  we  press  the  finger  on  one  eyeball,  do  we 
see  objects  double  ? 

"  Each  retina  possesses  regions  of  symmetry  with  the 
other,  and  on  this  fact  singleness  of  vision  depends; 
each  point  of  the  outer  portion  of  the  retina  of  the  right 
eye  has  its  point  of  symmetry  in  an  inner  portion  of  the 
left,  and  when  from  a  distant  object  rays  fall  on  these 
symmetrical  points,  that  object  will  be  seen  single  ;  but 
if,  by  the  pressure  of  the  finger  or  otherwise,  we  compel 
the  image  in  one  of  the  eyes  to  fall  upon  another 
and  non-symmetrical  point,  the  object  at  once  becomes 
double." 

(See  Draper's  Human  Physiology^  p.  395.) 

45.  Why  does  a  distant  light,  in  (lie  night,  seem  like  a 
star? 

The  light  radiating  in  every  direction  produces  the 
star-like  effect,  and  we  cannot  see  the  surrounding  objects 
by  which  to  correct  the  impression.  Hence  one  often 
mistakes  a  fire  on  a  distant  hill  for  a  star  rising. 


IN  PHYSICS.  2  1 9 

46.  Why  does  a  bright  light,  in  the  night,  seem  so  much 
nearer  than  it  is  ? 

We  judge  of  the  distance  of  an  object  by  its  magni- 
tude, by  its  distinctness  of  outline,  and  by  the  size,  etc., 
of  intervening  objects  with  which  we  compare  it.  In  the 
night,  the  brightness  of  a  light  confuses  us  by  its  vivid- 
ness, seeming  to  be  near  at  hand.  Moreover,  we  cannot 
see  the  neighboring  objects,  whose  distance  we  know  or 
could  estimate  in  the  daylight.  Our  error  is  therefore 
one  of  judgment.  A  firo  at  night  thus  seems  near  at 
hand,  and  persons  often  run  toward  it  for  great  distances, 
expecting  every  moment  to  reach  it. 

(See  Question  54.) 

48,  49.  (See  Key,  p.  40  ;  Questions  47,  48.) 

50.  Why  is  the  lens  of  a  fish's  eye  (seen  in  the  eye-socket 
of  a  boiled  fish)  so  convex  ? 

The  difference  of  density  between  the  water  and  the 
eye  is  not  so  great  as  that  between  the  air  and  the  eye. 
Hence,  to  refract  the  light  sufficiently  to  bring  it  to  a 
focus  on  the  retina  requires  a  more  convex  lens. 

(See  Dudgeon,  on  the  Human  Eye  ;  and  Physics,  p.  268,  note.) 

51.  When  do  the  eyes  of  a  portrait  seem  to  follow  a 
spectator  to  all  parts  of  a  room  ? 

This  is  noticed  only  in  a  full-face  portrait.  In  that 
case  the  spectator,  when  he  goes  to  either  side,  fails  to 
see  the  side  of  the  eyeballs,  and  hence  the  effect  is  that 
of  looking  directly  into  the  eye.  "  A  rifleman,  portrayed 
as  if  taking  aim  directly  in  front  of  the  picture,  appears 
to  every  observer  to  be  pointing  at  him  specially." 

5  2 .    Why  does  the  dome  cf  ike  sky  seem  flattened  ? 


220  ANSWEHS   TO   PRACTICAL   QUESTIONS 

"  Because  the  light  from  above,  having  to  pass  through 
a  less  amount  of  air,  is  less  obstructed  than  that  which 
comes  horizontally.  It  is  therefore  more  vivid." 

53.  Why  do  the  two  parallel  tracks  of  a  railroad  appear 
to  approach  in  the  distance  ? 

This  depends  upon  what  is  known  in  painting  as  the 
vanishing  point.  "  Suppose  two  long  rows  of  pillars,  100 
feet  apart,  and  an  observer  standing  at  one  end  looking 
down  the  rows.  Evidently,  for  the  same  reason  as  the 
space  between  the  top  and  bottom  of  the  pillars,  that  is 
to  say  their  height,  becomes  apparently  less  and  less  as 
their  distance  from  the  eye  increases,  so  will  the  space 
between  each  pillar  and  its  opposite  in  the  ether  row 
become  apparently  less,  and  the  lines  of  pillars  will,  at  a 
certain  distance  (viz.,  where  200  feet  are  apparently 
reduced  to  a  poinO,  seem  to  join.  Beyond  that  spot, 
known  as  the  vanishing  point,  none  of  the  pillars  can  be 
seen." 

(Read  Arnott's  Physics,  pp.  616-622.) 

54.  Why  does  a  fog  magnify  objects  ? 

The  fog  diminishes  the  intensity  of  the  light.  The 
visual  angle,  however,  remains  the  same.  "  An  object  at 
two  miles,  subtending  the  same  angle  as  an  object  at  one 
mile,  is  twice  as  broad,  and  the  conclusion  is  drawn  that 
the  dim  object  is  large.  Thus,  a  person  in  a  fog  may 
believe  that  he  is  approaching  a  great  tree  fifty  yards 
distant,  when  the  next  instant  throws  him  into  a  low 
bush  that  has  deceived  him.  A  boy  on  the  stage,  with 
a  thin  gauze  screen  before  him,  will  look  to  the  audience 
like  a  man  in  the  distance." 

(See  Arnott's  Physics,  p.  6a8.) 


IN  PHYSICS.  221 

It  is  not  the  refraction  of  the  rays  of  light,  as  is  com- 
monly supposed,  which  makes  an  object  seem  larger 
when  seen  through  a  mist.  It  really  appears  to  us  in  its 
proper  size.  The  mist,  however,  dims  the  color  and  the 
outline,  giving  it  the  indistinctness  belonging  to  a  mile 
in  distance,  while  it  has  the  magnitude  of  half  a  mile. 
Dr.  Wayland  relates  that,  as  he  was  sailing  through 
Newport  harbor  early  one  morning,  in  a  dense  fog,  he 
observed  on  the  apparently  distant  wharf  some  very  tall 
men.  While  he  was  remarking  upon  their  extraordinary 
size,  he  was  astonished  to  see  them  jumping  about  like 
children,  and  otherwise  behaving  in  a  most  unaccountable 
manner.  Presently,  as  the  sun  dispersed  the  fog,  he 
found  that  he  was  close  to  the  wharf,  and  that  the 
gigantic  men  were  really  a  party  of  small  boys  amusing 
themselves  with  play. 

The  opposite  mistake  is  made  when  the  atmosphere  is 
more  transparent  than  that  to  which  we  are  accustomed. 
Foreign  travellers  in  Switzerland,  who  have  started  on 
foot  to  visit  a  glacier  or  a  mountain-peak  which  seemed 
within  easy  distance,  have  often  been  surprised  to  find, 
after  two  or  three  hours  of  brisk  walking,  that  the  object 
of  their  desire  seemed  as  far  away  as  at  first.  So  in 
looking  across  a  sheet  of  water,  where  there  are  no 
intervening  objects,  distance  is  always  underrated. 

When  we  throw  a  stone  at  an  object  in  the  water  we 
find  that  our  eye  has  deceived  us,  and  the  stone  falls  far 
short  of  the  mark.  For  the  same  reason,  objects  seen 
on  the  shore  from  the  water  seem  much  less  than  their 
natural  size.  The  fact  is,  they  appear  of  the  magnitude 
which  belongs  to  the  distance,  but  we  suppose  the  distance 
less  than  it  is ;  and,  associating  this  magnitude  with  dimin- 
ished distance,  they  appear  to  us  less  then  they  really  are. 


222  ANSWERS  TO  PRACTICAL   QUESTIONS 

In  order  to  form  these  judgments  correctly,  one  of 
these  elements  must  be  fixed.  From  this  we  learn  to 
institute  a  comparison,  and  thus  form  an  accurate 
opinion.  If  we  know  the  magnitude  of  an  object,  the 
change  in  its  color  and  outline  will  teach  us  its  distance. 
If  we  know  its  distance,  we  can  judge  of  its  magnitude. 
Hence,  painters,  in  order  to  give  us  a  correct  idea  of  an 
object  which  they  represent,  always  place  in  its  vicinity 
something  with  whose  real  magnitude  we  are  familiar. 
Thus,  to  show  the  size  of  a  pyramid,  an  Arab  with  his 
camel  may  be  drawn  at  its  foot.  If  the  pyramid  were 
represented  by  itself,  its  intended  size  might  be  mistaken  ; 
but  every  one  knows  the  size  of  a  camel,  and  from  this 
he  would  judge  of  the  magnitude  of  a  pyramid. —  Way- 
land1  s  Intellectual  Philosophy,  p.  78,  et  seq. 

55.  If  you  sit  where  you   cannot  see  another  person's 
image,  why  cannot  that  person  see  yours  ? 

The  angle  of  incidence  is  equal  to  the  angle  of  reflec- 
tion under  all  circumstances.  If  a  ray  from  the  other 
person  is  not  reflected  at  the  right  angle  to  reach  your 
eye,  then  a  ray  from  you  is  not  reflected  at  the  right 
angle  to  reach  the  other  person's  eye. 

56.  Why  can  we  see  the  multiple  images  in  a  mirror 
better  if  we  look  into  it  very  obliquely  ? 

More  light  is  then  reflected  to  the  eye. 

(See  Physics )  p.  151,  2d  note.) 

57.  Why  is  an  image  seen  in  water  inverted'} 

(Examine  Fig.  140,  in  Physics.) 

58.  Why  is  the  surfs  light  fainter  at  sunset  than  at  mid- 
day? 

(See  Physics,  p.  149,  note.) 


IN  PHT81C8.  223 

59.  Why  can  we  not  see  the  fence-posts  when  we  are 
riding  rapidly  ? 

There  is  not  time  for  the  rays  of  light  to  produce  a 
distinct  impression  on  the  retina. 

(See  Physics,  p.  177,  line  13.) 

60.  Ought  a  red  flower  to  be  placed  in  a  bouquet  by  an 
orange  one  ?     A  pink  or  blue  with  a  violet  one  ? 

(See  Physics,  p.  167.) 

These  are  not  complementary  colors,  and  so  weaken 
rather  than  strengthen  each  other. 

6 1.  Why  are  the  clouds  white  while  the  clear  sky  is  blue1} 

Prof.  Tyndall  has  shown  that  the  larger  particles  of 
vapor  scatter  light  of  all  colors,  /.  e.,  white  light ;  while 
the  smallest  particles,  only  the  blue  rays.  In  accordance 
with  this  fact  the  clouds  are  white  and  the  sky  is  blue. 
If  the  air  were  absolutely  pure  and  free  from  all  foreign 
matter,  it  is  thought  that  the  azure  of  the  sky  would  not 
be  seen  and  the  heavens  would  appear  black :  the  illu- 
mination of  objects  would  be  strong  and  glaring  on  one 
side,  and  on  the  opposite  side  the  shadows  would  be 
deep  and  unrelieved  by  the  diffused  ,  light  to  which  we 
are  accustomed.  The  minute  particles  of  vapor  in  the 
air  serve  to  scatter  the  direct  rays  of  the  sun  and  to 
turn  them  around  corners  and  into  places  not  in  the 
direct  line  of  the  sunlight. 

(See  a  full  and  interesting  discussion  in  Tyndall's  Lecture  on  Light,  page 
152,  et  seq.) 

62.  Why  does  skim-milk  look  blue  and  new  milk  white? 

The  fatty  globules  of  the  new  milk  reflect  all  the 
colors  of  the  spectrum  to  the  eye ;  but  when  deprived 


224  ANSWEES  TO  PRACTICAL   QUESTIONS 

of  the  cream  the  milk  reflects  the  blue  light  in  excess 
of  the  others. 

63.  What  would  be  the  effect  of  filling  the  basin,  in  the 
experiment  shown  in  Fig.  147,  with  salt  water! 

The  water  would  be  made  denser  and  its  refractive 
power  would  be  correspondingly  increased. 

(Compare  Physics,  p.  268,  note.) 

64.  Why  is  not  the  image  of  the  sun  in  water  at  mid- 
day so  bright  as  near  sunset  ? 

(See  Physics,  p.  151,  ad  note.) 

65.  Why  is  the  rainbow  always  opposite  the  sun  ? 

(See  Physics,  p.  166.) 


HEAT. 

203. — 1-54.  (See  Key,  pp.  40-47.)  With  regard  to 
Question  23  there  is  much  difference  of  opinion.  Many 
authorities  think  that  temperature,  and  not  moisture,  is 
the  chief  factor  in  producing  barometric  changes. 

(See  Muller,  Komische  Physik,  637.) 

55.  Why  will  "fanning"  cool  the  face? 

It  brings  in  contact  with  the  face  a  current  of  fresh 
and  generally  cooler  air. 

(See  Physics,  p.  191.) 

56.  How  are  safes  made  fire-proof  1 

By  filling  the  space  between  the  inner  and  the  outer 
iron-plates  with  a  non-conducting  material,  as  plaster, 
etc.,  the  safe  is  rendered  nearly  fire-proof.  In  one  form 


IN  PHYSICS.  225 

of  safe>  pipes  of  water  are  used,  which  absorb  the  heat 
and  render  it  latent. 

57.  Why  can  you  heat  water  quicker  in  a  tin  than  a 
china  cup  ? 

Because  the  metal  is  a  better  conductor  of  heat  than 
the  china. 

58.  Why  will" a  woollen  blanket  keep  ice  from  melting? 
The  woollen  is  a  non-conductor  of  heat. 

59.  Does  dew  form  under  trees  ? 

The  trees  reflect  back  the  heat  radiated  by  the  earth, 
grass,  etc.,  and  so  prevent  the  temperature,  in  general, 
from  sinking  to  the  dew-point. 

60.  What  is  the  principle  of  heating  by  steam  ? 

(See  P&yszcs,  p.  206.) 

6 1.  Why  is  a  gun  firing  blank  cartridges  more  heated 
than  one  firing  balls  ? 

(See  Key,  p.  207,  Question  53.) 

62.  What  is  the  cause  of  "  cloud-capped"  mountains  ? 

(See  Physics,  p.  197.) 

63.  Show  how  the  glass  in  a  hot-house  acts  as  a  trap  to 
catch  the  sunbeam. 

(See  Physics,  p.  194.) 

64.  Does  the  heat  of  the  sun  come  in  through  our  win- 
dows ? 

(See  Physics,  p.  194.) 

65.  Does  the  heat  of  our  stoves  pass  out  in  the  same 
way? 

(See  Pkysics,  p.  194.) 


226  ANSWERS  TO  PRACTICAL  QUESTIONS 

67.  Is  a  dusty  boot  hotter  to  the  foot  than  a  polished  one  ? 

(See  Physics^  p.  194.) 

68.  The  top  of  a  mountain  is  nearer  the  sun  ;  why  is  it 
not  warmer  ? 

(See  Question  62.) 

72.  Can  we  find  frost  on  the  windows  and  on  the  stone- 
flagging  the  same  morning  ? 

It  requires  a  much  intenser  cold  to  produce  the  former 
effect  than  the  latter,  as  glass  is  a  poorer  conductor  of 
heat  than  stone.  We  frequently  find  frost  on  the  flagging 
early  in  the  fall,  but  frost  on  the  window  is  a  sign  of  very 
severe  winter  weather. 

73.  Why  will  not  snow  "pack"  into 'balls  except  in  mild 
weather  ? 

The  snow  must  be  very  near  the  melting-point  for  the 
pressure  of  the  hand  to  be  sufficient  to  melt  enough  of 
it  to  produce  the  phenomena  of  regelation.  (Physics, 
p.  202,  ist  note;  also  Tait's  Recent  Advances  in  Physical 
Science,  p.  129,  and  TyndalFs  Forms  of  Water,  p.  163.) 
This  principle  involves  the  theory  of  Glaciers.  "The 
masses  of  snow  cannot  rest  on  the  steep  slopes  of 
Alpine  summits.  The  pressure  upon  the  under  layers  is 
too  great  to  allow  them  to  remain  upon  their  sloping 
beds,  and  they  are  forced  to  descend.  This  descent  is 
accomplished  in  two  forms-:  that  of  an  avalanche,  one  of 
the  most  awful  and  imposing  spectacles  to  witness  ;  or  of 
a  glacier,  which  is  really  an  avalanche  of  ice  of  extremely 
slow  motion.  But  the  glacier  differs  from  the  ordinary 
avalanche  not  only  in  that  its  motion  is  so  slow,  but  in 
that  it  consists  of  ice,  thick,  firm,  and  hard.  The  prin- 
ciples involved  in  this  transition  of  the  loose,  flaky 


IN  PHYSICS.  227 

snow  which  first  falls  upon  the  mountain-top  into  the 
solid  ice  of  the  glacier,  are  very  well  illustrated,  as  Helm- 
holtz  has  remarked,  in  the  manufacture  of  the  school- 
boy's snow-ball  or  snow-man.  Very  cold  snow  is  always 
light  and  flaky,  and  cannot  be  made  by  the  pressure  of 
the  hands  into  a  cohesive  mass  ;  in  order  to  succeed  in 
that  operation,  snow  is  always  employed  which  is  already 
at  the  melting-point,  or  only  so  far  below  this  temperature 
that  the  warmth  of  the  hand  suffices  to  bring  it  to  the 
required  temperature,  and  then,  by  dint  of  pressure  and 
moulding,  an  icy  ball  may  be  easily  produced.  So  with 
the  formation  of  the  glacier  ice.  A  process  of  almost 
simultaneous  melting  and  freezing  goes  on  among  the 
under  layers  of  snow,  and  under  an  immense  and  ever- 
constant  pressure  from  the  weight  of  the  snow  above  j 
thus  solid  ice  is  formed.  That  this  ice  conforms  itself  to 
the  various  windings,  constrictions,  and  dilatations  of  its 
rocky  channel  during  its  downward  march  is  a  fact  not 
less  familiar  than  wonderful." 

74.  Why  is  the  sheet  of  zinc  under  a  stove  so  apt  to 
become  puckered  ? 

When  zinc  cools  after  expansion  it  does  not  return 
quite  to  its  former  dimensions,  and  so  becomes  "  puck- 
ered," as  it  is  called. 

75.  Why  does  a  mist  gather  in  the  receiver  of  the  air- 
pump  as  the  air  becomes  rarefied  ? 

"The  remaining  air,  cooled  by  rarefaction,  absorbs 
heat  from  the  invisible  vapor  in  combination  with  it,  and 
renders  the  water  visible.  The  mist  may  be  removed  by 
continued  action  of  the  machine,  or  by  readmitting  the 
normal  quantity  of  air." 

(See  Arnott's  Physics,  p.  448.) 


228  ANSWERS  TO  PRACTICAL   QUESTIONS 

76.    Why  are  the  tops  of  high  mountains  in  the  tropics 
covered  with  perpetual  snow  I 

(See  Question  62.) 


MISCELLANEOUS    QUESTIONS    AND   -PROB- 
LEMS   FOR   REVIEW. 

1.  Does  a  plumb-line  point  to  the  earth's  centre  of  figure 
"*•  Centre  of  gravity  ? 

2.  In  a  dark  room,  let  the  light  of  a  candle  pass  through 
a  small  hole  in  a  card,  and  the  image  of  the  candle  on  the 
opposite  wall  will  be  inverted.     Explain. 

3.  Why  does  drift  on  the  Mississippi  accumulate  for  the 
most  part  on  the  west  bank  ? 

4.  How  many  times  heavier  is  the  earth  than  an  equally 
large  globe  of  water  ? 

5.  Why  does  the  arc  of  a  rainbow  seem  a  part  of  an 
ellipse  instead  of  a  circle  ? 

6.  Why  does  a  rocket  ascend  into  the  air  ? 

7.  Is  the  water  at  the  foot  of  Niagara  Falls   warmer 
than  that  in  the  river  above  ? 

8.  What  causes  wheel  fire-works  to  rotate  ? 

9.  A  brass-rod  covered  tightly  with  thin  paper  may  be 
held  some  time  in  a  fiame  without  the  paper  being  scorched ; 
while,  if  the  rod  be  of  wood,  the  paper  will  scorch  at  once. 
Why  is  this  difference  ? 

10.  How  would  it  affect  the  action  of  a  siphon  if  it  were 
carried  up  a  mountain  ? 


IN  PHYSICS.  229 

11.  If  a  vessel  of  water  containing  a  floating  body  be 
placed  under  the  receiver  of  an   air-pump,  and  the  air 
gradually  exhausted,  what  will  be  the  effect  on  the  floating 
body? 

12.  How  will  it  change  the  height  of  the  column  of 
mercury  in  a  barometer  to  incline  the  tube  ? 

13.  In  the  image  of  a  written  page  seen  in  a  mirror,  why 
does  the  writing  seem  to  slope  to  the  left  ? 

14.  Why  does  a  coin  placed  in  a  tumbler  look  i*r&jr 
when  the  glass  is  full  of  water  than  when  it  is  empty  ? 

15.  Two  bodies  of  different  bulks  weigh   the  same  in 
water;  which  will  weigh  the  more  in  mercury,  the  larger  or 
the  smaller  ? 

1 6.  flow  does  the  wind  drift  sand,  snow,  etc.  ? 

1 7.  Why  does  oil  "  still  troubled  waters  "  ? 

• 

1 8.  Why  does  crouching  down  at  the  highest  points  in  a 
swing,  and  standing  up  at  the  lowest  point,  increase  the 
velocity  ? 

19.  What  difference  would  it  make  in  the  guinea-and- 
feather  experiment  to  force  into  the  tube  additional  air, 
instead  of  exhausting  it,  as  ordinarily  done  ? 


EXPLAINING  MIRRORS  AND  LENSES. 

The  author  has  met  with  the  best  success  in  explaining 
mirrors  and  lenses  to  his  pupils,  by  using  the  following 
method. 

A  Concave  Mirror. — Holding  up  before  his  eye  the  fore- 
finger of  each  hand,  he  represents  to  the  pupil  how  the  rays 
of  light  enter  his  eye  converging ;  how  he  then  sees  the  ob- 
ject on  diverging  rays  :  thus  the  ^visual  angle  being  increased, 
the  apparent  size  of  the  object  is  correspondingly  increased. 
By  crossing  his  two  forefingers  before  his  eye  he  represents 
the  focus,  and  shows  how  diverging  rays  then  enter  the  eye  ; 
the  object  is  seen  on  converging  rays,  the  visual  angle  is  de- 
creased, and  the  apparent  size  of  the  object  correspondingly 
decreased. 

A  Convex  Mirror. — Using  the  fingers  in  the  same  way,  he 
illustrates  how  diverging  rays  enter  the  eye,  the  object  is  seen 
on  converging  rays,  the  visual  angle  is  diminished,  and  the 
apparent  size  of  the  object  correspondingly  diminished.  The 
rays  of  light  are  not  brought  to  a  focus,  hence  the  second  ef- 
fect of  a  concave  mirror  cannot  be  seen. 

The  same  illustration  can  be  used  in  explaining  lenses, 
remembering  that  the  effect  of  a  convex  lens  is  like  that  of  a 
concave  mirror,  and  of  a  concave  lens  that  of  a  convex  mirror. 

At  the  close  of  the  explanation  and  illustration  with  the 
fingers,  the  following  formula  is  put  on  the  blackboard,  and 
the  pupil  applies  it  to  each  class  of  mirrors  and  lenses  : 

CONVERGING   (diverging)   RAYS  ENTER  THE   EYE,   THE 

OBJECT  IS  SEEN  ON  DIVERGING  (converging)  RAYS  ;  HENCE 
THE  VISUAL  ANGLE  IS  INCREASED  (decreased),  AND  THE 
IMAGE  IS  LARGER  (smaller)  THAN  LIFE. 


THE  NATIONAL  SERIES  OF  TEXT-BOOKS. 


THE     NATIONAL    READERS. 

By    PARKER    &    WATSON. 

No.  i. — National   Primer, 6t.pp.,i6mo, 

No.  2. — National  First  Reader,   .     .     .  f28pp.,?6mo, 

No.  3. — National  Second  Reader,  .     .  224. pp., 

No.  4. — National  Third   Reader,      .     .  288pp., 

No.  5. —  National  Fourth  Reader,*.     .  £32  pp.,  /2mo, 

No.  6. — National  Fifth   Reader,  .     .     .  600  pp.,  f2mo, 


National  Elementary  Speller,       .     .     .     feo  pp.,  f6mo, 
National   Pronouncing  Speller,   .     .     .     188pp.,  t2mo, 


THE     INDEPENDENT    READERS. 

By  J.    MADISON    WATSON. 

The  Independent  First  (primary)   Reader,   so  pp.,  f6mo, 

The  Independent  Seconcf  Reader,  .  16O pp., 

The  Independent  Third   Reader,     .  .  2&o pp., 

The  Independent  Fourth   Reader,  .  .  26!,. PP.,  I2mo, 

The  Independent  Fifth   Reader,      .  .  336pp.,  f2mo, 

The  Independent  Sixth  Reader,      •.  .  tflpp.,  t2mo, 

The  Independent  Complete  Speller,  .  162 pp., 


The  Independent  Child's  Speller  (Script),   so  pp., 
The  Independent  Youth's  Speller  (Script),  tea  pp.,  f2mo, 


National  Series  of  Standard  School-Sootes. 

ENGLISH    GRAMMAR. 


CLARK'S    DIAGRAM    SYSTEM. 


Ciark's  Easy  Lessons  in  Language, 

Published  1874.  Contains  illustrated  object-lessons  of  the  moet  attractive  charac. 
ter,  and  is  couched  in  language  freed  as  much  as  possible  from  the  dry  technicalities 
of  the  science. 

Clark's  Brief  English  Grammar, 

Published  1872.  Part  I.  is  adapted  to  youngest  learners,  and  the  whole  forms  a 
complete  •'  brief  course  "  in  one  volume,  adequate  to  the  wants  of  the  common 
school. 

Clark's  Normal  Grammar, 

Published  1870,  and  designed  to  take  the  place  of  Prof.  Clark's  veteran  "Prac- 
tical" Grammar,  though  the  latter  is  still  furnished  upon  order.  The  Normal  is 
an  entirely  new  treatise.  It  is  a  full  exposition  of  the  system  as  described  below, 
with  all  the  most  recent  improvements.  Some  of  its  peculiarities  are— A  happy 
blending  of  SYNTHESES  with  ANALYSES  ;  thorough  Criticisms  of  common  errora 
in  the  use  of  our  Language ;  and  important  improvements  in  the  Syntax  of  Sen- 
tences and  of  Phrases. 

Clark's  Key  to  the  Diagrams, 

Clark's  Analysis  of  the  English  Language,  • 

Clark's  Grammatical  Chart, 

The  theory  and  practice  of  teaching  grammar  in  American  schools  is  meeting 
with  a  thorough  revolution  from  the  use  of  this  system.  While  the  old  method* 
offer  proficiency  to  the  pupil  only  after  much  weary  plodding  and  dull  memorizing, 
this  affords  from  the  inception  the  advantage  of  practical  Object^  Teaching,  address- 
ing the  eye  by  means  of  illustrative  figures  ;  furnishes  association  to  the  m2mory, 
Its  most  powerful  aid,  and  diverts  the  pupil  by  taxing  his  ingenuity.  Teachers 
who  are  using  Clark's  Grammar  uniformly  testify  that  they  and  their  pupils  find  it 
the  most  interesting  study  of  the  bchoo!  course. 

Like  all  great  arid  radical  improvements,  the  system  naturally  met  at  first  with 
much  unreasonable  opposition.  It  has  not  onty  outlived  the  greater  part  of  this 
opposition,  but  finds  many  of  its  warmest  admirers  among  those  who  could  not 
at  first  tolerate  so  radical  an  innovation.  All  it  wants  is  an  impartial  trial  to  con- 
vince the  most  skeptical  of  its  merit.  No  one  who  has  fairly  and  intelligently, 
tested  it  in  the  school-room  has  ever  been  known  to  go  back  to  the  old  method.} 
A  great  success  is  already  established,  and  it  is  easy  to  prophecy  that  the  day  is 
not  far  distant  when  it  will  be  the  only  system  of  teaching  English  Grammar.  A» 
the  SYSTEM  is  copyrighted,  no  other  text-books  can  appropriate  this  obvious  nni 
great  improvement. 


Welch's  Analysis  of  the  English  Sentence, 

assif 
Leon 

10 


Remarkable  for  its  new  and  simple  classification,  its  method  of  treating  conneo. 
«vea,  its  explanations  of  the  idioms  and  constructive  laws  of  the  language,  etc. 


The  National  Series  of  Standard  ScAool-'Boofcs. 

GEOGRAPHY. 


NATIONAL  GEOGRAPHICAL  SYSTEM. 

THE   SERIES. 

/.  Monteith's  First  Lessons  in  Geography, 
II.  Monteith's  New  Manual  of  Geography, 
II.  McNally's  System  of  Geography, 

INTERMEDIATE  OR   ALTERNATE  VOLUMES. 

I*.  Monteith's  Introduction  to  Geography, 

2*.  Monteith's  Physical  and  Political  Geography, 

ACCESSORIES. 

Monteith's  Wall  Maps  2  sets  (see  page  15), 
Monteith's  Manual  of  Map- Drawing  (Allen's  System) 
Monteith's  Map-Drawing  and  Object-Lessons, 
Monteith's  Map-Drawing  Scale, 

1,  PRACTICAL  OBJECT  TEACHING^ The  infant  scholar  is  first  Introduce^ 
to  a  picture  whence  he  may  derive  notions  of  the  shape  of  the  earth,  the  phenom 
ena  of  day  and  night,  the  distribution  of  land  and  water,  and  the  great  natural 
divisions,  which  mere  words  would  fail  entirely  to  convey  to  the  untutored  inind. 
Other  pictures  follow  on  the  same  plan,  and  the  child's  mind  is  called  upon  to  grasp 
QO  idea  without  the  aid  of  a  pictorial  illustration.     Carried  on   to  the  higher 
books,  this  system  culminates  in  Physical  Geography,  where  such  matters  as 
climates,  ocean  currents,  the  winds,  peculiarities  of  the  earth's  cruet,  clouds  and 
rain,  are  pictorially  explained  and  rendered  apparent  to  the  most  obtuse.    The 
illustrations  used  for  this  purpose  belong  to  the  highest  grade  of  art. 

2,  CLEAR,  BEAUTIFUL,  AND  CORRECT  MAPS,    In  the  lower  numbers  the 
maps  avoid  unnecessary  detail,  while  respectively  progressive,  and  affording  the 
pupil  new  matter  for  acquisition  each  time  he  approaches  in  the  constantly  en- 
larging  circle  the  point  of  coincidence  with  previous  lessons  in  the  more  ele« 
mentary  books.  In  tiie  Physical  and  Political  Geography  the  maps  embrace  many 
new  and  striking  features.    One  of  the  most  effective  of  these  is  the  new  plan  for 
displaying  on  each  map  the  relative  sizes  of  countries  not  represented,  thus  obvi- 
ating  much  confusion  which  has  arisen  from  the  necessity  of  presenting  maps  iq 
tiie  same  atlas  drawn  on  different  scales.  The  maps  of  "  McNally"  have  long  been 
celebrated  for  their  superior  beauty  and  completeness.    This  is  the  only  school- 
book  in  which  the  attempt  to  make  a  complete  atlas  also  clear  and  distinct,  ha» 
been  successful.     The  map  coloring  throughout  the  eeries  is  also  noticeable. 
Oelic&te  and  subdued  tints  take  the  place  of  the  startling  glare  of  Inharmonious 
colors  which  too  frequently  in  such  treatises  dazzle  the  eyes,  distract  the  atten- 
tion, and  serve  to  overwhelm  the  names  of  towns  and  the  natural  feature*  of  tb» 


The  National  Series  of  Standard 

GEOGRAPHY-Continued, 

MONTEITH'S   INDEPENDENT   COURSE. 
Elementary  Geography 
Comprehensive  Geography  (with  103  Maps) 

These  volumes  are  not  revisions  of  old  works— not  an  addition  to  any 


series— but  are  entirely  new  productions— each  by  itself  complete,  independent, 
comprehensive,  yet  simple,  brief,  cheap,  and  popular ;  or,  taken  together,  the  most 
admirable  "  series  "  ever  offered  for  a  common-school  course.  They  present  the 
following  features,  skillfully  interwoven — the  student  learning  all  about  one  country 
at  a  time. 

LOCAL  GEOGRAPHY,  or  the  Use  of  Maps.  Important  features  of 
the  Maps  are  the  coloring  of  States  as  objects,  and  the  ingenious  system  for  laying 
down  a  much  larger  number  of  names  for  reference  than  are  found  on  any  other 
Maps  of  same  size— and  without  crowding. 

PHYSICAL  GEOGRAPHY,  or  the  Natural  Features  of  the  Earth, 
Illustrated  by  the  original  and  striking  Relief  Maps,  being  bird's-eye  views  or 
photographic  pictures  of  the  Earth's  surface. 

DESCRIPTIVE  GEOGRAPHY,  including  the  Physical ;  with  some 
account  of  Governments,  and  Races,  Animals,  etc. 

HISTORICAL  GEOGRAPHY,  or  a  brief  summary  of  the  salient 
ooints  of  history,  explaining  the  present  distribution  of  nations,  origin  of  geo- 
graphical names,  etc. 

MATHEMATICAL  GEOGRAPHY,  including  ASTRONOMICAL. 
which  describes  the  Earth's  position  and  character  among  planets  ;  also  the  Zones. 
Parallels,  etc. 

COMPARATIVE  GEOGRAPHY,  or  a  system  of  analogy,  con- 
necting  new  lessons  with  the  previous  ones.  Comparative  sizes  and  latitudes  arc 
ehown  on  the  margin  of  each  Map,  and  all  countries  are  measured  in  the  "frain* 


TOPICAL  GEOGRAPHY,  consisting  of  questions  for  review,  an<J 
testing  the  student's  general  and  specific  knowledge  of  the  subject,  with  sugges- 
tions for  Geographical  Compositions. 

ANCIENT  GEOGRAPHY.  A  section  devoted  to  this  subject,  with 
Maps,  will  be  appreciated  by  teachers.  It  is  seldom  taught  in  our  common  schools, 
because  it  has  heretofore  required  the  purchase  of  a  separate  book. 

GRAPHIC  GEOGRAPHY,  or  MAP-DBAWTNG  by  Allen's  "Unit  oi 
Measurement"  system  (now  almost  universally  recognized  as  without  a  rival)  is 
introduced  throughout  the  lessons,  and  not  as  an  appendix. 

CONSTRUCTIVE  GEOGRAPHY,  or  GLOBE-MAKING.  With  eacX 
book  a  set  of  Map  Segments  is  furnished,  with  which  each  student  may  make  hia 
own  Globe  by  following  the  directions  given. 

RAILROAD   GEOGRAPHY,  with  a  grand  Map  illustrating  route* 

af  travel  in  the  United  States.    Also,  a  "  Tour  in  Europe." 

14 


The  National  Series  of  Standard  School-Sco&s. 

MATHEMATICS. 


DAVIES'  NATIONAL  COURSE. 

ARITHMETIC. 

!l.  Davies'  Primary  Arithmetic, 

2.  Davies'  Intellectual  Arithmetic, 

3.  Davies'  Elements  of  Written  Arithmetic, . 

4.  Davies'  Practical  Arithmetic, 

5.  Davies'  University  Arithmetic. 

TWO  BOOK  SERIES. 
I.  First  Book  in  Arithmetic,  Primary  and  Me^taL 
2.  Complete  Arithmetic. 

ALGEBRA. 

1.  Davies'  New  Elementary  Algebra. 

2.  Davies'  University  Algebra, 

3.  Davies'  New  Bourdon's  Algebra. 

GEOMETRY. 

1.  Davies'  Elementary  Geometry  and  Trigonometry, 

2.  Davies'  Legendre's  Geometry, 

3.  Davies'  Analytical  Geometry  and  Calculus, 

4.  Davies'  Descriptive  Geometry, 
4.  Davies'  New  Calculus, 

MENSURATION. 

I.  Davies'  Practical  Mathematics  and  Mensuration, 

2.  Davies'  Elements  of  Surveying, 

3.  Davies'  Shades,  Shadows,  and  Perspective, 

MATHEMATICAL    SCIENCE 

Davies'  Grammar  of  Arithmetic, 

Davies'  Outlines  of  Mathematical  Science, 

Davies'  Nature  and  Utility  of  Mathematics,  ' 

Davies'  Metric  System,  t 

Oavies  &  Peck's  Dictionary  of  Mathematics, 

17 


The  National  Series  of  Standard  School-Books. 

MATHEMATICS— Continued. 

PECK'S    HIGHER    COURSE. 

Peck's  Manual  of  Algebra, 

Bringing  the  methods  of  Bourdon  within  the  range  of  the  Academic  Course. 

Peck's  Manual  of  Geometry, 

By  a  method  purely  practical,  and  unembarrassed  by  the  details  which  rather 
confuse  than  simplify  science. 

Peck's  Practical  Calculus, 
Peck's  Analytical  Geometry^ 
Peck's  Elementary  Mechanics, 
Peck's  Mechanics,  with  Calculus, 

The  briefest  treatises  on  these  subjects  now  published.  Adopted  by  the  great 
Universities;  Yale,  Harvard,  Columbia,  Princeton,  Cornell,  &c. 

ARITHMETICAL    EXAMPLES. 
Reuck's  Examples  in   Denominate  Numbers, 
Reuck's  Examples  in  Arithmetic, 

These  volumes  differ  from  the  ordinary  arithmetic  in  their  peculiarly  practical 
character.  They  are  composed  mainly  of  examples,  and  afford  the  most  severe  and 
thorough  discipline  for  the  mind.  While  a  book  which  should  contain  a  complete 
treatise  of  theory  and  practice  would  be  too  cumbersome  for  every-day  us«»,  the 
insufficiency  of  practical  examples  has  been  a  source  of  complaint. 

HIGHER    MATHEMATICS. 

Macnie's  Algebraical  Equations, 

Serving  as  a  complement  to  the  more  advanced  treatises  on  Algebra,  giving  spe- 
cial attention  to  the  analysis  and  solution  of  equations  with  numerical  coefficients. 

Church's  Elements  of  Calculus, 
Church's  Analytical   Geometry, 
Church's  Descriptive  Geometry,  2  vols.. 

These  volumes  constitute  the  "West  Point  Course"  in  their  several  department*. 

Courtenay's  Elements  of  Calculus, 

A  standard  work  of  the  very  highest  grade. 

Hackley's  Trigonometry, 

With  applications  to  navigation  and  surveying,  nautical  and  practical  geometry 
and  geodesy. 


The  National  Series  of  Standard  School- 

HISTORY-Continued, 

BARNES'  ONE-TERM  HISTORY 
A  Brief  History  of  the  United  Stales, 

This  is  probably  the  MOST  ORIGINAL  SCHOOL-BOOK  published  for  many  years 
in  any  department.    A  few  of  its  claims  are  the  following: 

1.  Brevity.— The   text  is  complete    for   Grammar  School  or  intermediate 
classes,  in  290  12mo  pages,  large  type.    It  may  readily  be  completed,  if  desired,  ia 
one  term  of  study. 

2.  Comprehensiveness,— Though  so  brief,  this  book  contains  the  pith  of  all 
the  wearying  contents  of  the  larger  manuals,  and  a  great  deal  more  than  the  mem- 
ory usually  retains  from  the  latter. 

3.  Interest  has  been  a  prime  consideration.     Small  books  have  heretofore 
been  bare,  full  of  dry  statistics,  unattractive.    This  one  is  charmingly  written, 
replete  with  anecdote,  and  brilliant  with  illustration. 

1  Proportion  Of  Events. -It  is  remarkable  for  the  discrimination  with 
which  the  different  portions  of  our  history  are  presented  according  to  their  im- 
portance. Thus  the  older  works  being  already  large  books  when  the  civil  war 
took  place,  give  it  less  space  than  that  accorded  to  the  Revolution. 

5.  Arrangement. — In  six  epochs,  entitled  respectively,  Discovery  and  Settle- 
ment, the  Colonies,  the  Revolution,  Growth  of  States,  the  Civil  War,  and  Current 
Events. 

6.  Catch  Words. — Each  paragraph  is  preceded  by  its  leading  thought  in 
prominent  type,  steading  in  the  student's  mind  for  the  whole  paragraph. 

7.  Key  Notes. — Analogous  with  this  is  the  idea  of  grouping  battles,  etc. 
about  some  central  event,  which  relieves  the  eameness  go  common  in  such  de- 
scriptions, and  renders  each  distinct  by  some  striking  peculiarity  of  its  own. 

8.  Foot  Notes.— These  are  crowded  with    interesting  matter   that  is  not 
strictly  a  part  of  history  proper.    They  may  be  learned  or  nbt,  at  pleasure.    They 
are  certain  in  any  event  to  be  read. 

9.  Biographies  of  all  the  leading  characters  are  given  in  full  in  foot-notes. 

10.  Maps.— Elegant  and  distinct  Maps  from  engravings  on  copper-plate,  and 
beautifully  "colored,  precede  each  epoch,  and  contain  all  the  places  named. 

11.  Questions  are  at  the  back  of  the  book,  to  compel  a  more  independent  use 
of  the  text.    Both  text  and  questions  are  so  worded  that  the  pupil  must  give  in. 
telligrent  answers  IK  HIS  OWN  WORDS.    "  Yes"  and  *'No"  will  not  do. 


12.  Historical  Recreations.— These  are  additional  questions  to  test  the  stu- 
dent's knowledge,  in  review,  as  :  "  What  trees  are  celebrated  in  our  history  ?" 
"  When  did  a  fog  save  our  army  ?  "     "  What  Presidents  died  in  office  ? "    "  When 
was  the  Mississippi  our  western  boundary  ?  "    "  Who  said,  '  I  would  rather  be 
right  than  President  ? '  "  etc. 

13.  Th3  Illustrations,   about  seventy  in  number,  are  the  work  of  pur  best 
artists  and  engravers,  produced  at  great  expense.     They  are  vivid  and  interest- 
ing, and  mostly  upon  subjects  never  before  illustrated  in  a  school-book. 

11  Dates.— Only  the  leading  dates  are  given  in  the  text,  and  these  are  so 
associated  as  to  assist  the  memory,  but  at  the  head  of  each  page  is  the  date  of  the 
event  first  mentioned,  and  at  the  close  of  each  epoch  a  summary  of  events  and  dates. 

15.  The  Philosophy  Of  History  is  studiously  exhibited— the  causes  and 
effects  of  events  being  distinctly  traced  and  their  interconnection  shown. 

16.  Impartiality.  —  All  sectional,  partisan,  or  denominational    views  are 
avoided.     Facts  are  stated  after  a  careful  comparison  of  all  authorities  without 
the  least  prejudice  or  favor. 

17.  Index.— A  verbal  indent  at  the  close  of  the  book  perfects  it  as  a  work  of 
reference. 

It  will  be  observed  that  the  above  are  all  particular?  <n  which  School  Fl^tories 
have  been  signally  defective,  or  altogether  wanting.  Many  other  claims  t«  Ifcvoi 
U  shares  in  common  with  its  predecessors. 

24 


The  National  Series  of  Standard  School- 33ooks. 

NATURAL    SCIENCE. 
"FOUKTEEN  WEEKS"  IN  EACH  BRANCH, 

By  J,  DORMAN  STEELE,  A.M. 

Steele's    14  Weeks  Course  in  Chemistry  (New  Ed.) 
Steele's   14  Weeks  Course  in  Astronomy 

Steele's  14  Weeks  Course  in  Philosophy 

Steele's  14  Weeks  Course  in  Geology 

Steele's   14  Weeks  Course  in  Physiology 

Steele's   14  Weeks  Course  in  Zoology 

Steele's   14  Weeks  Course    in  Botany 

Our  Text-Booki  in  those  studies  are,  as  a  general  thing,  dull  and  uninteresting. 
They  contain  from  400  to  600  pages  of  diy  facts  and  unconnected  details.  Tl^y 
abound  in  that  which  the  student  cannot  learn,  much  less  remember.  The  paj'ii 
commences  the  study,  is  confused  by  the  fine  print  and  coarse  print,  and  neither 
knowing  exactly  what  to  learn  nor  what  to  hasten  over,  is  crowded  through  the 
single  term  generally  assigned  to  each  branch,  and  frequently  comes  to  the  clooe 
without  a  definite  and  exact  idea  of  a  single  scientific  principle. 

Steele's  Fourteen  Weeks  Courses  contain  only  that  which  every  well-informed 
person  should  know,  while  all  that  which  concerns  only  the  professional  scientist 
is  omitted.  The  language  is  clear,  simple,  and  interesting,  and  the  illustrations 
bring  the  subject  within  the  range  of  home  life  and  daily  experience.  They  give 
such  of  the  generaf  principles  and  the  prominent  facts  as  a  pupil  can  make  famil- 
iar as  household  words  within  a  single  term.  The  type  is  large  and  open ;  there 
is  no  fine  print  to  annoy ;  the  cuts  are  copies  of  genuine  experiments  or  natural 
phenomena,  and  are  of  fine  execution. 

In  fine,  by  a  system  of  condensation  peculiarly  his  own,  the  author  reduces  each 
branch  to  the  limits  of  a  single  term  of  study,  while  sacrificing  nothing  that  is  es- 
sential, and  nothing  that  is  usually  retained  from  the  study  of  the  larger  manuals 
in  common  use.  Thus  the  student  has  rare  opportunity  to  economize  his  time,  or 
rather  to  employ  that  which  he  has  to  the  best  advantage. 

A  notable  feature  is  the  author's  charming  "  style,"  fortified  by  an  enthusiasm 
over  his  aabject  in  which  the  student  will  not  fail  to  partake.  Believing  that 
Natural  Science  is  full  of  fascination,  he  has  moulded  it  into  a  form  that  attracts 
the  attention  and  kindles  the  enthusiasm  of  the  pupil. 

The  recent  editions  contain  the  author's  "  Practical  Questions  "  on  a  plan  never 
before  attempted  in  scientific  text-books.  These  are  questions  as  to  the  nature 
and  cause  of  common  phenomena,  and  are  not  directly  answered  in  the  text,  the 
design  being  to  test  and  promote  an  intelligent  use  of  the  student's  knowledge  of 
the  foregoing  principles. 

Steele's  General    Key  to  his  Works,       .     .     .     .     .     $1.00 

This  work  is  mainly  composed  of  Answers  to  the  Practical  Questions,  and  Solu- 
tions of  the  Problems,  in  the  author's  celebrated  "Fourteen  Weeks  Courses  "  in 
the  several  sciences,  with  many  hints  to  teachers,  minor  Tables,  &c.  Should  be 
on  every  teacher's  desk. 

34 


The  Natio?tal  Series  of  Standard  School-Books  * 

ELOCUTION. 

Thwing's  Vocal  Culture. 

A  Drill- Book  for  voice  and  gesture,  by  Eev.  Prof.  Thwing,  of  Brooklyn  Tabernacle 
Lay  College.  Price  50  cts. 

Taverner  Graham's  Reasonable  Elocution, 

Based  upon  the  belief  that  true  Elocution  is  the  right  interpretation  of  THOUGHT, 
and  guiding  the  student  to  an  intelligent  appreciation,  Instead  of  a  merely  uechaii- 
ical  knowledge,  of  its  rules. 

Zachos1  Analytic  Elocution. 

All  departments  of  elocution— such  as  the  analysis  of  the  voice  and  the  sentence, 
phonology,  rhythm,  expression,  gesture,  etc. — are  here  arranged  for  instruction  iu 
classes,  illustrated  by  copious  examples. 

Sherwood's  Self  Culture. 

Self-culture  in  reading,  speaking,  and  conversation— a  very  valuable  treatise  to 
those  who  would  perfect  themselves  in  these  accomplishments. 

SPEAKERS. 

Northend's  Little  Orator,    .  &0.40     Child's  Speaker,     .    $0.40 

Two  little  works  of  the  same  grade  but  different  selections,  containing  simple  and 
attractive  pieces  for  children  uuuer  twelve  years  of  age. 

Northend's  Young  Declaimer,    $0.50     National  Orator,  .         70 

Two  volumes  of  Prose,  Poetry,  and  Dialogue,  adapted  to  intermediate  and  gram- 
mar classes  respectively. 

Northend's  Entertaining  Dialogues,    ...'....         70 
Extracts  eminently  adapted  to  cultivate  the  dramatic  faculties,  as  well  as  entertain. 

Oakey's   Dialogues  and  Conversations, 60 

For  School  Exercises  and  Exhibitions,  combining  useful  instruction. 

James's  Southern   Selections  for  Reading  and  Oratory,        1.10 

Embracing  exclusively  Southern  literature. 

Swett's  Common   School   Speaker, 90 

Raymond's  Patriotic  Speaker, 1.25 

A  superb  compilation  of  modern  eloquence  and  poetry,  with  original  dramatic  ex- 
ercises. Nearly  every  eminent  modern  orator  is  represented. 

COMPOSITION     AND     RHETORIC. 
Brookfield's  First  Book  in  Composition,    .     .     .     .     .      $0.35 

Making  the  cultivation  of  this  important  art  feasible  for  the  smallest  child.  By  a 
new  method,  to  induce  and  stimulate  thought. 

Boyd's  Composition  and   Rhetoric, 1.00 

This  work  furnishes  all  the  aid  that  is  needfal  or  can  be  desired  in  the  various  de- 
partments and  styles  of  composition,  both  in  prose  and  verse. 

Day's  Art  of   Rhetoric, 00 

Noted  for  exactness  of  definition,  clear  limitation,  and  philosophical  development 
of  subject ;  the  large  share  of  attention  given  to  Invention,  as  a  branch  of  Rhetoric, 
mid  the  unequalled 'analysis  of  style. 

38 


National  Series  of  Standard 


PUNCTUATION. 
Cocker's  Hand-Book  of  Punctuation  ......     $0.50 

With  Instructions  for  Capitalization,  Letter-Writing  and  Procf-Reading.  Most 
works  on  this  subject  are  so  abstruse  and  technical  that  the  unprofessional  reader 
finds  them  difficult  of  comprehension  ;  but  this  little  treatise  is  so  simple  and  com- 
prehensive that  persons  of  very  ordinary  intelligence  caii  readily  understand  and 
apply  its  principles. 

MIND     AND     MORALS. 
Mahan's    Intellectual    Philosophy     .......     1.25 

The  subject  exhaustively  considered.  The  author  has  evinced  learning,  candor, 
and  independent  thinking. 

Mahan's  Science  of    Logic      .........     1.40 

A  profound  analysis  of  the  laws  of  thought.  The  system  possesses  the  merit  of 
being  intelligible  and  self-consistent.  In  addition  to  the  author's  carefully  elabo- 
rated views,  it  embraces  results  attained  by  the  ablest  minds  of  Great  Britain,  Ger- 
many and  France,  in  this  department. 

Boyd's  Elements  of    Logic      .........     0.90 

A  systematic  and  philosophic  condensation  of  the  subject,  fortified  with  additions 
from  Watts,  Abercrombic,  Whately,  &c. 

Watts  on  the    Mind      ...........      0.35 

The  Improvement  of  the  Mind,  by  Isaac  Watts,  is  designed  as  a  guide  for  the  at- 
tainment of  useful  knowledge.    As  a  text-book  it  is  unparalleled  ;   and  the  disci- 
pline it  affords  cannot  be  too  highly  esteemed  by  the  educator. 
—  »t  •»  ••»  — 

Peabody's   Moral    Philosophy     ....     .....     0.90 

A  short  course  ;  by  the  Professor  of  Christian  Morals,  Harvard  University—  for 
the  Freshman  Class  and,  for  High  Schools. 

Alden's  Text-Book  of    Ethics     .........     0.40 

For  young  pupils.  To  aid  in  systematizing  the  ethical  teachings  of  the  Bible,  and 
point  out  the  coincidences  between  the  instructions  of  the  sacred  volume  and  the 
sound  conclusions  of  reason. 

Wil  lard's   Morals  for  the  Young     .     .     .     .....     0.50 

Lessons  in  conversational  style  to  indicate  the  elements  of  moral  philosophy. 
The  study  is  made  attractive  by  narratives  and  engravings. 


GOVERNMENT. 
Howe's  Young  Citizen's  Catechism        0.50 

Explaining  the  duties  of  District,  Town,  City,  County,  State,  and  United  States 
Officers,  with  rules  for  parliamentary  and  commercial  business. 

Young's   Lessons  in   Civil   Government 0.90 

A  comprehensive  view  of  Government,  and  abstract  of  the  laws  showing  the 
rights,  duties,  and  responsibilities  of  citizens. 

Mansfield's   Political   Manual „      .     0.90 

This  is  a  complete  view  of  the  theory  and  practice  of  the  General  and  State  Gov- 
ernments, designed  as  a  text-book.  The  author  is  an  esteemed  and  able  professor  of 
constitutional  law,  widely  known  for  his  sagacious  utterances  in  the  public  press. 

Martin's  Civil    Government      .      . 0.90 

Emanating  from  Massachusetts  State  "Normal  School.  Historical  and  statistical. 
Each  chapter  summarized  by  a  succinct  statement  of  underlying  principles  on  which 
good  government  is  based. 

Gallaudet's  International    Law 0.90 

Published  1879,  and  the  only  work  bringing  the  subject  within  the  compass  of  a 
convenient  text-book, 

39 


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THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


